A bully to a bawdy-house; one who is kept in pay, to oblige the frequenters of the house to submit to the impositions of the mother abbess, or bawd; and who also sometimes pretends to be the husband of one of the ladies, and under that pretence extorts money from greenhorns, or ignorant young men, whom he finds with her. See Greenhorn.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Bully * Bully CockNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes