Last winter, the World Oral Literature Project at the University of Cambridge released a list of 3,524 dead and dying languages. Among the 150 considered to be in “extremely ­critical ­condition” were Southern Pomo (spoken by Native Americans in California), Gamilaraay (from New South Wales), Mócheno (northern Italy), Istriot (the Croatian coast), and Manx (the Isle of Man). The entry that drew the most attention, perhaps because its speakers are not defined by geography, was Polari, an underground language used by gay men in London until the 1970s.

The existence of a “gay language” is not well known, even in the U.K. A poll of British gay men in 2000 revealed that half of respondents had never heard of it. If Polari is known outside of England, it is most likely because Morrissey once titled an album Bona Drag, which means “nice outfit.” And there is a brief Polari scene—with subtitles—in the 1998 film Velvet Goldmine (“A tart, my dears, a tart in gildy clobber!”). But you’d have to scour a lot of pubs to find anyone who still uses it in conversation. When the Cambridge list came out, Paul Baker, the leading Polari scholar, was surprised that it had been considered endangered, not extinct.

And yet the news of Polari’s demise contained a deeper question: is it a language at all? Most speakers would have considered it no more than a lexicon, designed to trip up outsiders and amuse insiders. As Morrissey sings in “Piccadilly Palare,” from Bona Drag: “The Piccadilly Palare was just a silly slang / Between me and the boys in my gang. / ‘So bona to vada, oh you, / Your lovely eek and your lovely riah.’ / We plied an ancient trade / Where we threw all life’s instructions away.”

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Playful as it is, Polari grew out of punishing circumstances. When it first gained popularity in London, in the mid-twentieth century, homosexuality was a crime that the police were eager to prosecute, and blackmailing was rampant. In a famously tragic case, in 1952 Alan Turing, the cryptanalyst who cracked the Germans’ Enigma code, was caught having an affair with a man. After being tried for gross indecency, he agreed to a “treatment” of female-hormone injections, then committed suicide in 1954.

Given these appalling conditions, embattled homosexuals needed a means to communicate. As Baker writes in Polari—The Lost Language of Gay Men (2002), Polari was “a way of tearing down ‘heterosexual’ reality, and remoulding it as a world seen through gay eyes, with gay standards.” Its users tended to be flamboyant working-class “queens”—arch eccentrics in the model of Quentin Crisp, with rouged cheeks and flashy scarves. Or they were married men with offices in the West End who used Polari to pick up “trades” on the sly. Or pent-up sailors in the Merchant Navy, known to the land folk as “seafood.” Or male prostitutes who hung around Piccadilly Circus, which Polari speakers simply called “the dilly.”

For these men, Polari was ­verbal safe space, a kind of Jabberwocky for the marginalized. Still, Baker is divided as to whether it can be classified as a language. On the one hand, it can differ from English on the level of ­syntax—Naff feeley ­hommie translates as “I’m very jealous of that young man.” On the other, its vocabulary is too specialized to function independently. “It may be ideal for gossiping about potential sexual ­conquests on the gay scene,” Baker writes, “but outside this genre its usefulness becomes less viable.”

Baker considers several alternative categories: slang, pidgin, ­creole, sociolect. He settles, hesitantly, on “anti-language,” a corollary to the idea of an “anti-society,” which he defines as “a conscious alternative to society, existing by resisting ­either passively or by more hostile, destructive means.” Language ­elevates society; anti-language subverts it. (­Another example is Grypsera, a
dialect of Polish prisoners.)

Despite the hardships under which it flourished, Polari is radiantly funny. Its sensibility combines the droll humor of Cockney rhyming slang with the bitchiness of drag queens. Let’s start with the basics: bona for good, ducky for dear. A man was an omee and a woman was a palone, which meant that a gay man was an omee-palone and a lesbian was a palone-omee.

It’s often said (falsely) that Eskimos have many words for snow, a phenomenon known as over-lexicalization. Unsurprisingly, ­Polari has a glut of words for homosexual (queen, nelly, duchess), sex (arva, charver, troll), and police, who were trivialized with femme put-downs (betty bracelets, lillian law, jennifer justice). Body parts were particularly well named: lallies for legs, ogles for eyes, lappers for hands, pots for teeth, and aris (short for Aristotle) for arse. Other words were borrowed from backslang: riah for hair and ecaf (or eek) for face.

Then there are dozens of wry phrases, such as the colour of his eyes (penis size) and cleaning the kitchen (oral or anal sex). Your mother’s a stretcher-case translates as “I’m tired.” A manly alice was a masculine homosexual. One might be described as a size queen, a sea queen, a blasé queen, or a black-market queen. To zhoosh the riah was to comb one’s hair. A sexually available man was TBH, or to be had. Anything tasteless or undesirable was naff. (Originally used as a pejorative term for “heterosexual,” the word became popular among its targets, who adopted it into mainstream British slang.)

If it sounds like Polari is just a sassy version of English, consider what happens when you string it all together: “‘So sister,’ I polaried. ‘Will you take a varder at the cartz on the feely-omi in the naf strides; the one with the bona blue ogles over there polarying the omi-palone with a vogue on and the cod sheitel.’” (Translation: “‘So friend,’ I said. ‘Will you check out the package on that young man in the ugly trousers; the one with the pretty blue eyes over there talking with the gay guy with the cigarette and the bad wig.’”)

That passage, from James Gardiner’s Who’s a Pretty Boy Then?, hints at one of the main uses of ­Polari: gossiping about other men. It’s no coincidence that the most common verb is vada, or “look at.” Speaking in code, two queens riding a bus through town could size up the sailor across the aisle, or drop a flirtatious hint to a “black-market” businessman.

Baker traces Polari’s earliest roots to Thieves’ Cant, a language derived from Elizabethan pelting slang. Besides its panoply of words for lawbreaker (prigger of prancers, jarkman, bawdy basket), Cant used the word cheat to rename body parts—smelling cheat for nose, hearing cheat for ear—a formulation that trickled down to Polari. (A ­rogering cheat is a penis.) In the eighteenth century, British gay culture centered around Molly Houses—private clubs where effete men would gather and pair off. The “Mollies” had a vernacular of their own, including, for sex, riding a rump, the pleasant deed, and caudle making.

Since the Mollies were subject to imprisonment, their speaking patterns naturally overlapped with those of Cant. Both ­dialects fed into Polari’s direct predecessor, Parlyaree, a nineteenth-century slang popular among ­actors and circus performers. Because theater people were low on the ­social ladder, they mixed with all sorts of gypsies, tramps, and thieves. In a ­Parlyaree song cited by the lexicographer Eric Partridge, a busker plots to evade his landlord:  “­Nantee ­dinarlee: The omee of the carsey / Says due bion peroney, ­manjaree on the cross / We’ll all have to scarper the jetty in the morning, / Before the bonee omee of the carsey shakes his doss.”

Nineteenth-century England saw an influx of Italian street performers, which might account for Polari’s clear Italian influence, in words like bona, manjaree, and polari itself (from parlare, or “to speak”). Baker also finds traces of Romani, Yiddish, and lingua franca, the common tongue of Mediterranean ports. It seems that every itinerant group, from Jews to organ-grinders, shaped Polari, including the American GIs who flooded England during World War II. When they departed, they left behind Yankee slang. It is to them that Polari owes blow job, cruise, and butch.

So why didn’t America have its own gay language? The conditions were just as bad, and the need for secrecy just as pressing. Of course, there was slang—a way of speaking that James McCourt, the author of Queer Street: Rise and Fall of an American Culture, 1947–1985, recalls as “very zippy, very fast, with lots of repartee.” Men would call each other “Mary” or “Hilda.” On their way to the bathhouse, they’d say that they were “going to ­Midnight Mass at the Cathedral”—a reference to the rumored homosexual Cardinal Spellman.

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But in the gay pockets of New York and San Francisco in the ’50s, language was not the primary means of code. “It was tone of voice, intonation, more than actual words,” McCourt recalls. Men would communicate in stares and glances, cruising each other at designated stalls or bookstores. They would meet for sex in the Ramble in Central Park, or in the dunes of Fire Island. There was no need for newfangled words—just the cover of night.

Perhaps Britain, in its ancientness, is more prone to linguistic variation. Polari wouldn’t have existed had not Parlyaree, Cockney, and Italian converged on England’s fairgrounds. Tellingly, a gay argot emerged concurrently in South ­Africa, which is similarly rich in languages. The dialect, called Gayle, has elements of English, Afrikaans, and, yes, Polari.

By the ’60s, British culture began to thaw, and Polari morphed from underground pickup slang to a defiant means of self-expression. “We flaunted our sexuality,” one speaker recalled, in 1979. “We were pleased to be different. We were proud and secretly longed to broadcast our difference to the world.”

Even so, it’s remarkable that Polari’s two most famous representatives came into ­prominence while homosexuality was still illegal. Their names were Julian and Sandy, a fictional pair of out-of-work actors played with panache by Hugh Paddick and Kenneth Williams. Every Sunday afternoon from 1964 to 1969, they were featured on the BBC radio series Round the Horne, a variety show hosted by the comedian Kenneth Horne. Julian and Sandy’s act always came last, and it was always the most popular. Their fans ranged from members of the Royal Ballet to young boys in provincial towns, who would fantasize about the louche London life.

Not that the duo was explicit about their sexuality. Much of the ribald humor of the Julian and Sandy sketches stems from innuendo. Typically, a segment would revolve around a new shop or business that Mr. Horne would patronize. Upon arrival, he would discover its two outrageous proprietors, who were simply moonlighting between acting gigs. In one installment, Mr. Horne visits a legal establishment called “Bona Law,” looking for help with a parking ticket. Julian isn’t sure if they can take the case: “We’ve got a criminal practice that takes up most of our time.”

Speaking in Polari-infused English, Julian and Sandy introduced the wider world to terms like riah, omee-palone, and eek. They also used Polari to get racy jokes past the censors. In one sketch, Julian says innocently, “All the dishes are dirty,” to which an offended Sandy responds, “Speak for yourself!” The savvy listener might have known that dish was slang for “attractive person.” But only the initiated would have known it could also mean “asshole.”

In their banter, Julian and Sandy hinted at a seedy social milieu. They gabbed about their choreographer friend Reynard La Spoon and a hunky masseuse named Gordon. (“He’ll give you a good pummeling, I’ll tell you!”) Mr. Horne was their “straight man” in both senses. If he ever hinted at some knowledge of Polari, the boys would make insinuating remarks:

Julian: We are the Cecil B’s of the 16 De Mille.

Sandy: Yes.

Julian: Small-budget pictures, really.

Mr. Horne: Would I have vadered any of them, do you think?

Sandy: Oooh! He’s got all the Polari, hasn’t he?

Julian: I wonder where he picks it up?

Amazingly, the humor of Julian and Sandy still holds up. They’re naughty but lovable, with a flair for double entendre. Yes, they were stereotypes of campy queens, but they gave the rest of England a taste of the dilly. Like Glee and Will & Grace decades later, they were just palatable enough for the masses, but smart enough to be subversive:

Sandy: Don’t mention Malaga to Julian, he got very badly stung.

Mr. Horne: Portuguese man-o’-war?

Julian: Well, I never saw him in uniform.

Paradoxically, Julian and Sandy’s popularity only hastened Polari’s demise. Once the average Londoner knew what an omee-palone was, the jig was up. The Polari on Round the Horne was bare-bones, but it was catchy enough to undermine its own usefulness. As Baker writes, Polari got “publicised out of existence.”

That wasn’t all that changed. In 1967, the same year that Round the Horne won a Writers’ Guild of Great Britain Award, the Sexual Offences Act legalized homosexuality for consenting adults. The Stonewall riots in New York came two years later, bolstering the British gay-rights movement. Pubs and other businesses could cater openly to gay men, giving rise to the notion of the “pink pound”—gay disposable income. With all that pride, who needed a secret language?

In the ’70s, Polari suffered an even bigger blow: a backlash against camp itself. To liberated gay men, fops like Julian and Sandy were seen as retrograde. With the advent of a new, hyper-masculine ideal (think of mustachioed porn stars and the Village People), the sexual currency of “queens” declined. The infamous hanky code—men would wear handkerchiefs in their back pockets, colored to specify their erotic tastes—made coded language ­obsolete. Polari became synonymous with ­minstrelsy, a ghettoizing holdover from a bygone era. By the ’80s, it was moribund. In 1999, the gay magazine Boyz compared it to Benny Hill imitating a Chinaman.

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In linguistics, there are several types of language death. Often a language dissolves gradually, as native speakers adapt to a dominant culture. Sometimes a conquest or government decree wipes out a vernacular overnight. Occasionally, there is a genocide. In the case of Polari, the gay community turned on its effeminate elders, essentially biting off its own tongue. In Polari’s decline, there are elements of “linguicide,” or what some linguists call “language murder.”

Unlike Southern Pomo, Polari has had a vibrant afterlife. In the past decade or so, a new generation has embraced it as part of “gay heritage,” sparking a Polari renaissance. There’s a gay journal called Polari Magazine, which features book reviews and marriage-equality news. The London nightclub Madame Jojo’s, home of the “Kitsch Cabaret,” encourages its staff to use words like omee and fantabulosa. The George, a gay bar in Dublin, has a neon sign that reads bona polaris. In London, the writer Paul Burston runs a “gay literary salon” called Polari, which the BBC described as “popular with the younger crowd.” If you take a train to Stoke-on-Trent, about an hour and a half outside of London, and look up the address 52 Piccadilly, you will find a coffee shop with a purple and rainbow banner called the Polari Lounge, which opened in 2010. There are menu items named after Polari words, and a beginner’s guide on each table. (Paul Baker stopped there recently and told the owner that he’d written books on the subject. The guy seemed uninterested.)

Polari no longer serves as an anti-language, because the anti-society has dissolved. It survives as a historical curiosity, full of retro charm. Whether that is a good thing depends on what you make of gay assimilation in general. The fight over gay marriage, for ­instance, has divided the gay community, some of whom have no interest in joining a mainstream institution. On the other hand, it’s perhaps too tempting to romanticize the old days, when separatism was a necessity, not a choice.

The highbrow appropriation of Polari is also ironic; as Baker told me, “It’s supposed to be bitchy and about sex.” Perhaps, in that last regard, Polari isn’t so different from any other language. After all, so much of speech stems from desire—the need to express what churns within the body and the heart. Sixty years ago, the desire was furtive, but Polari hid in plain sight. It stands as a testament to the creativity of confined spaces, and to the power of laughing in the face of powerlessness.