BLIND-HARPERS,
Canters, who counterfeit Blindness, strowl about with Harps, Fiddles, Bagpipes, &c. led by a Dog or Boy.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
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Blind Harpers in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).