A species of louse peculiar to the human body; the male is denominated a cock, the female a hen.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Crab Lanthorn * Crab ShellsNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes