To knock a woman; to have carnal knowledge of her. To knock off; to conclude: phrase borrowed from the blacksmith. To knock under; to submit.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Knob * Knock Me DownNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes