Green’s Dictionary of Slang

trucks n.

trousers.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1873		Sl. Dict.
1894		A. Morrison Tales of Mean Streets (1895) 91: Then he lifted a leg of the trousers hanging behind the door. ‘I’d bet a trifle,’ he said, ‘she made these ’ere trucks.’.
1908		Gem 17 Oct. 8: You’ve never liked him since the time he got his teeth into your trucks.