A yeoman of the guards, instituted by Henry VII. Their office was to stand near the bouffet, or cupboard, thence called Bouffetiers, since corrupted to Beef Eaters. Others suppose they obtained this name from the size of their persons, and the easiness of their duty, as having scarce more to do than to eat the king’s beef.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Beef * Beetle-browedNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes