Feet. To shake one’s trotters at Bilby’s ball, where the sheriff pays the fiddlers; perhaps the Bilboes ball, i.e. the ball of fetters: fetters and stocks were anciently called the bilboes.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Trot * To TrounceNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes