To bribe. To grease a man in the fist; to bribe him. To grease a fat sow in the a-se; to give to a rich man.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Gravy-eyed * Greasy ChinNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes