Ham, dried tongue, or some other salted meat, cut thin and put between two slices of bread and butter: said to be a favourite morsel with the Earl of Sandwich.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Sammy * Sandy PateNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes