Drummers of the foot guards, or Chelsea hospital, who find out weddings, and beat a point of war to serenade the new married couple, and thereby obtain money.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Crop-1 * CroppenNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes