A fool, or thick-sculled fellow; also, among printers the same as dung among journeymen taylors. See Dung.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Muckinder * Mud LarkNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes