Polari was once a slang used variously by actors, circus and fairground showmen, sailors, criminals, prostitutes and the gay subculture. It can be traced back to the 19th century (and possibly much earlier) and there is a long-standing connection with Punch and Judy who traditionally used Polari to converse. However it was falling into disuse by the mid-20th century and might have been lost were it not for the “Julian and Sandy” sketches from BBC Radio’s comedy series Round the Horne.
What is slightly surprising is how many Polari words have actually made it into mainstream English usage, sometimes today with a slightly distorted meaning, including:
barney — a fight
bijou — small, little
blag — pick up
butch — masculine lesbian
camp — effeminate
clobber — clothes
cottage — a public lavatory used for sexual encounters; hence cottaging
cove — friend
doss — bed
mince — walk affectedly
naff — awful, dull
ogle — look, admire
rough trade — a working class, tough, thuggish sex partner
scarper — to run off
troll — to walk about
There’s a lot more about Polari over on Outskirts of the Twenties, and of course on Wikipedia.