From Wikipedia:

Thieves’ cant was a secret language (or cryptolect) formerly used by thieves, beggars and hustlers of various kinds in Great Britain and to a lesser extent in other English-speaking countries. The classic, colorful argot is now mostly obsolete, and is largely relegated to the realm of literature and fantasy role-playing, although individual terms continue to be used in the criminal subcultures of both Britain and the U.S..

Here’s a sample:

Artichoke: hanged (see hearty choke)

Blue pigeons: thieves who steal lead off houses and other buildings

Charactered: to have your hand burnt as a punishment for theft

More here.