Green’s Dictionary of Slang

brace up v.

[? Fr. argot braser des faffes, to forge documents]

to pawn stolen goods.

[Aus]Vaux Vocab. of the Flash Lang.
[UK]A. Thornton Don Juan in London II 406: He braces up – but I forgot you’re not initiated – he receives stolen goods.
[UK]Hotten Dict. of Modern Sl. etc.
[UK]Hotten Sl. Dict.
[UK]Sl. Dict.
[UK]J. Ware Passing Eng. of the Victorian Era.