Green’s Dictionary of Slang

bullock’s (horn) n.

pawn.

1873		Sl. Dict.
a.1909		press cutting in J. Ware Passing Eng. of the Victorian Era 54/2: Put your kicksies in the bullock’s horn.
1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 2: Bullock’s horn: Pawn.
1953		J. Franklyn Cockney 293: [He] lost so heavily that he had to put his Dicky Dirt (shirt) in bullock’s horn (pawn).
1960		J. Franklyn Dict. of Rhy. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.