Rogues who, in changing money, by dexterity of hand frequently secrete two or three shillings out of the change of a guinea. This species of roguery is called the pinch, or pinching lay.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
To Pinch On the Parson’s Side * To PinkNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes