If we’re recommending con films the list isn’t complete without Stephen Frears and Donald Westlake’s adaptation of Jim Thompson’s The Grifters. Although set in 1980s Los Angeles, it anachronistically uses dialogue directly from Thompson’s novel including classic grifter jargon.
Stranger
Criminals have used argot to confuse those that might apprehend them for centuries; probably for as long as there have been criminals. One of the most developed is Polari, “*a mixture of Romance (Italian or Mediterranean Lingua Franca), Romani, London slang, backslang, rhyming slang, sailor slang, and thieves’ cant. Later it expanded to contain words from the Yiddish language and from 1960s drug subculture slang. *” It was widely adopted by the gay community in London in the 60s as homosexuality was illegal then.
It spread into the mainstream too, and some popular radio programmes used it for comic effect (it was said that the bosses at the BBC let it through because they had no idea how rude some of it was). Here is an example from “Round The Horne” in the 50s:
“Omies and palones of the jury, vada well at the eek of the poor ome who stands before you, his lallies trembling”
Translation: “Men and women of the jury, look well at the face of the poor man who stands before you, his legs trembling.”
Cant also fits.