Green’s Dictionary of Slang

(US black) a form of harness filled with bottles and used for the illicit sale of liquor in the street.

1945

D. Burley N.Y. Amsterdam News 24 Feb. 14A: Them old pre-war ‘walkies’. You know, that kind of harness which looks like a corset that you wear under your overcoat an’ which has a belt round the middle in which you have ten or twelve bottles of booze [...] You carry your glass in an inside coat pocket.