Green’s Dictionary of Slang

1. (also fair trade, free trade) smuggling.

1818		W. Perry London Guide.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 178: Trade [...] Free-trade ? smuggling; and so is Fair-trade.

2. burglary, robbery of any kind.

1742		Account of Behaviour, Confessions, and Dying Words 10/1: Mr. M—, who us’d to applaud him, and call Ben his best Boy, and say that he was worth fifty other Lads of the Trade; and [...] laid a wager of 10s. that Ben could commit more Robberies in two Nights, than any other Boy he could bring, could in a Week.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 178: Swindlers of goods, inquire about ‘the state of trade to-day?’ very much like regular paying persons. ‘What trade are you doing?’ ‘I have a prospect of doing something, or have a thing in hand,’ is the slangery of this species of rogue. [Ibid.] 216: Trade — any means of getting money, robbery not excepted.
1846		Swell’s Night Guide 59: Hang me up high! a lummy pitch. This ere Brighton’s a slashing walk of trade. Right as a jemmy! – mizzle’s the word.
1877		J. Greenwood Dick Temple I 219: ‘Then the man is a thief’ [...] ‘Served his time to the trade [...] been at it ever since he was a kid.’.