BULLY-COCK,
a Hector or bravo sets on People to quarrel, pretending to be a Second to them; and then making Advantage of both.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
Bully Cock in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).