Visitors to East London in search of a cash machine while attending the Olympics this past summer might have been puzzled by the ATM on Commercial Street. Tap the screen and a prompt pops up: English or Cockney? If Cockney is chosen, the next prompt advises the customer in search of "fast sausage and mash" (cash) to select the amount. Among the options: A "Lady Godiva" (£5), "speckled hen" (£10), or "horn of plenty" (£20), to be dispensed after the customer enters a "Huckleberry Finn" (pin). (Take a tour of East London with this photo gallery from National Geographic magazine.)

The shtick (not a Cockney word) was the idea of Bank Machine, an ATM operator based in the United Kingdom. "We wanted to introduce something fun and of local interest to our London machines," a company official explained when the machines were launched a few years ago. (Your London Pictures: See the city through the eyes of Nat Geo fans.)

No one is certain when Cockney rhyming slang became the verbal currency of East End London, but British lexicographer Jonathon Green, author of Cassell's Rhyming Slang, guesses it was around the 1820s or '30s. Rhyming slang, he says, was created by market traders, or costermongers, in part for the sheer pleasure of playing with language but also, more subversively, as a way of talking over the heads of authorities and the police. In Cockney rhyming slang, a common word is replaced by a rhyming phrase (traditionally, the secondary rhyming word is omitted). For example: To use your loaf (short for loaf of bread) in rhyming slang means to use your head.

Rhyming slang, says Green, who has spent his life career as its chronicler, is the dark side of language. "It is what Freud would call the id, or unfettered self," he says. "The themes are sex, insults, defecation, racism, nationalism, or calling someone mad, fat, or stupid." So it is with Cockney slang, where a "Johnny Bliss" is a piss.

Changing Scene, Changing Sounds

Is it still viable? East End London has changed. Displaced by the influx of immigrants, not to mention the metamorphosis of gentrification, the original East Enders, the Cockney white working class, have long since moved to outlying areas east or northwest of the city. These days in East London you may hear more than 200 different languages—Bengali, Urdu, and Swahili among others—and the lingua franca of the younger generation is something called Multicultural London English, a mix of West Indies, hip-hop, and bits and bobs of traditional Cockney.

Cockney rhyming slang hasn't disappeared, says Paul Kerswill, a professor in the University of York's Department of Language and Linguistics. "It's regenerating itself in new circumstances." And so it has. These days the ne plus ultra of fame is to have a Cockney rhyming slang sobriquet named after you: A "Britney Spears" (or a "Britney" for short) is a beer. "Posh and Becks" (celebrity couple Victoria Beckham, aka Posh Spice, and husband David Beckham) is Cockney slang for sex.