A secret slang let a persecuted community talk safely in plain earshot

Before homosexuality was decriminalized in Britain in 1967, gay men risked prison for it. Polari, a slang built from backslang, rhyming slang, Italian, Yiddish and circus and theatre jargon, let speakers signal identity and hold conversations in public without outsiders understanding. A BBC radio comedy briefly made it mainstream in the 1960s — which, ironically, helped kill it as a secret code.

— Community-developed argot, Polari — Britain, 19th-20th century; documented by Paul Baker