To DOCK,
to lie witha Woman. The Cull Docks the Dell in the Darkmans; the Rogue lay with the Wench all Night.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
To Dock in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).