The bowels. There is a rumpus among my bowels, i.e. I have the colic. The frill of a shirt.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Chit * Chitty-facedNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes