CANK,
Dumb. The Cull's Cank; the Rogue's Dumb; a Term used by Canters, when one of their Fraternity, being apprehended, upon Examination, confesses nothing.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
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Cank in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).