Green’s Dictionary of Slang

(UK Und.) to rob; thus spice the swell v., to rob the gentleman; spicing n., a street robbery.

a.1790		H.T. Potter New Dict. Cant (1795) n.p.: spicing footpad robbery.
1809		G. Andrewes Dict. Sl. and Cant [as cit. a.1790].
1811		Lex. Balatronicum n.p.: Spice. To rob. Spice the swell; rob the gentleman. [Ibid.] n.p.: The cove’s so scaly, he’d spice a malkin of his jazey: the fellow is so mean, that he would rob a scare-crow of his old wig.
1812		Vaux Vocab. of the Flash Lang. in McLachlan (1964) 267: spice the spice is the game of footpad robbery; describing an exploit of this nature; a rogue will say, I spiced a swell of so much, naming the booty obtained.
1821		Flash Dict. [as cit. a.1790].
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		Metropolitan Mag. XIV Sept. 333: For want of prads we were at first obliged to spice it.
1859		Matsell Vocabulum.