Small white specks under the finger nails, said to portend gifts or presents. A stingy man is said to be as full of gifts as a brazen horse of his farts.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
gibson * gift of the gabNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes