Green’s Dictionary of Slang

rap v.2

[? SE rap, to seize or snatch]

to swap, to exchange, to barter.

c.1698
170017501800
1823
[UK]B.E. Dict. Canting Crew n.p.: Rap to Swop or Exchange a Horse or Goods.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.