A luncheon, or snap before dinner: so called from its damping, or allaying, the appetite; eating and drinking, being, as the proverb wisely observes, apt to take away the appetite.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Damned Soul * Dance upon NothingNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes