A wicked debauched fellow; one of the ancient family of the sad dogs. Swift translates it into Latin by the words TRISTIS CANIS.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
sack * saddleNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes