Foul language, or abuse. Billingsgate is the market where the fishwomen assemble to purchase fish; and where, in their dealings and disputes, they are somewhat apt to leave decency and good manners a little on the left hand.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Bill of Sale * BingNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes