Definition - Informal language that consists of either new words or existing words used in a special sense.
Note: This is in contrast to jargon, which is a specific group's technical vocabulary.

Example -
The ankle-biter bailed (i.e. the child left).

Etymology -
According to the OED, the word's etymology is unknown.
Note: Some claim that it might derive from a Scandinavian language (e.g. from the Norwegian slengenamn, nickname, or slengja kjeften, to abuse with words. However, the OED believes that the "date and early associations of the word make it unlikely that there is any connection" with these Norwegian words).

Oxford English Dictionary -
The term's first citation in this sense is from 1818:
"Two of the best [students] come to me as a peculiar grinder (I must have a little slang)."
(Keble in Sir J. T. Coleridge Mem. (1869), 75)

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