A fat woman. He has got the wrong sow by the ear, he mistakes his man. Drunk as David’s sow; see DAVID’S SOW.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Souse * Sow’s BabyNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes