SET,
as Dead Set, a Term used by Thief-catchers when they have a Certainty of seizing zome of their Clients, in order to bring them to Justice.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
Set in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).