CATCHING-HARVEST,
a precarious Time for Robbery; when many People are out upon the Road, by means of any adjacent Fair, Horse-race, &c.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
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Catching Harvest in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).