BUNG-NIPPERS,
Cut purses, who with a short sharp Knife, and a horn Thumb, used to cut Purses. Since the wearing of Purses is out of Fashion, they are called Files or Pick-Pockets.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
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The Vulgar Tongue originally collected by Grose, 1811.
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).