A servant belonging to the Temple and Gray’s Inn, whose office is to announce the dinner. This in the Temple, is done by blowing a horn; and in Gray’s Inn proclaiming the word Manger, Manger, Manger, in each of the three courts.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Pannam * PannyNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes