Green’s Dictionary of Slang

a plot, a villainous scheme.

1725		New Canting Dict. n.p.: scrap a Design, a purpos’d Villainy, a vile intention; also a perpetrated Roguery: He whiddles the whole Scrap; He discovers all he knows.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. 1725].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant n.p.: Scrapp, a villainous scheme.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
1859		Matsell Vocabulum.