A daring, resolute fellow. In Germany and Flanders the boldest dogs used to hunt the boar, having a kind of buff doublet buttoned on their bodies, Rubens has represented several so equipped, so has Sneyders.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Dog Buffers * DogNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes