Bits and pieces of Romany or Rom, the language of the itinerant Gypsies, were incorporated into street slang among the lower classes, particularly ThievesCant. HenryMayhew seems to have thought these terms were from Latin (see ThievesCant), but I supect, given that Rom is so close to Latin, that he was wrong about this.
If anyone has a good source on RomanySlang, please put it here!
-- ChrisLehrich? - 30 Dec 2004