I just learned a useful term from Wikipedia: “An anti-language or cant is the language of a social group which develops as a means of preventing people from outside the group understanding it. […] Examples of anti-languages include cockney rhyming slang, CB slang, the grypsera of Polish prisons, thieves’ cant, Polari, and possibly Bangime. The concept was studied by the linguist M. A. K. Halliday who used the term for the lingua franca of an anti-society which is set up within another society, as a conscious alternative to it, and which indicates linguistic accomplishments of the users in action.” My problem is that I’m not sure how it’s supposed to differ from a cryptolect. Is anyone familiar enough with this stuff to clarify (if indeed there is a significant difference)?
(By the way, we discussed Polari back in 2003.)