Those whose fathers were clapperdogens, or beggars born, and who themselves follow the same trade: the female sort beg with a number of children, borrowing them, if they have not a sufficient number of their own, and making them cry by pinching in order to excite charity; the males make artificial sores on different parts of their bodies, to move compassion.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
To Palaver * PallNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes