Green’s Dictionary of Slang

a coat pocket.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
1833		‘The Chummies’ Society’ in Fun Alive O! 53: I’m a Master Sweep, you must all know, / With plenty of cash in my gropuses.
1841		‘Ax My Eye’ Dublin Comic Songster 101: With them wi’ empty gropusses, / I sports my ochre like a brick.
1846		G.W.M. Reynolds Mysteries of London I 36/2: My eye! what a slap up lily bejamin he had on when he was nabbed [...] and sich a swell bandana fogle in the gropus.
1848		Flash Dict. in Sinks of London Laid Open.