A fair. The drop coves maced the joskins at the gaff; the ring-droppers cheated the countryman at the fair.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Gad-so * To GaffNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes