slang: [18] Slang is a mystery word. It first appeared in underworld argot of the mid-18th century. It had a range of meanings – ‘cant’, ‘nonsense’, ‘line of business’, and, as a verb, ‘defraud’. Most of these have died out, but ‘cant’ is the lineal ancestor of the word’s modern meaning. It is not clear where it came from, although the use of the verb slang for ‘abuse’, and the expression slanging match ‘abusive argument’, suggest some connection with Norwegian dialect sleng- ‘offensive language’ (found only in compounds).
