A Welch rabbit; bread and cheese toasted, i.e. a Welch rare bit. Rabbits were also a sort of wooden canns to drink out of, now out of use.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
quota * rabbit catcherNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes