A common name for a rabbit, also for the monosyllable. To touch bun for luck; a practice observed among sailors going on a cruize.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Bumping * BundlingNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes