Slang, I wrote recently, is a perennially active frontier of language, where words and usages emerge, spread, mutate, and typically fade – though some are eventually assimilated into the common vocabulary.
Overlapping with slang is thieves’ cant, the old jargon of the underworld. The more general sense of cant is insincere talk: affected language often used with an assumption of piety or moral high ground. But in philology, cant refers to the sublanguage of street criminals and people on the fringes of society, such as gypsies, hobos, beggars and rogues.
Cant has been more spoken than written, and its precise origins are, unsurprisingly, shrouded in uncertainty. But it was once a vibrant vocabulary that served not only to identify someone as part of the subculture but to prevent those outside it from understanding the speaker.
Historically, this crooked corner of English met with considerable lexicographic interest. Early dialectologists seeking fresh slang for their collections would pay late-night visits to disreputable areas, partly out of linguistic interest but also as a service to society. George Andrewes wrote, in the blurb to his Dictionary of the Slang and Cant Languages (1809):
One great misfortune to which the Public are liable, is, that Thieves have a Language of their own; by which means they associate together in the streets, without fear of being over-heard or understood.
The idea was that by becoming acquainted with thieves’ and scoundrels’ “mysterious Phrases” we might more easily detect and deter their villainous activity. Richard Head’s Canting Academy (1673), one of the earliest books of this type, was similarly motivated to share the “hidden and mysterious” speech of the underworld.
Browsing the late-17th-century A New Dictionary of the Terms Ancient and Modern of the Canting Crew, we encounter the familiar cobble (“to mend or patch”), the ironic marriage-music (“children’s cries”), the onomatopoeic thwack (“to beat with a stick”), and the uncommon pea-goose (“silly creature”), arsworm (“a little diminutive fellow”), rum-dubber (“expert picker of locks”), and priggers of the cacklers (“poultry-stealers”).