Green’s Dictionary of Slang

trouser v.

to pocket.

1865		G.A. Sala My Diary in America II 63: Not a clerk in the Custom House [...] drew his pay without being contemplated by some candidate for office, muttering: ‘Next year, or the year after next, I shall trouser the dollars of that cuss, I guess’.
1885		Bulletin (Sydney) 29 Aug. 10/2: [I]f there be any truth in the rumour, we have a shrewd suspicion that the eloquent (and otherwise gifted) parson must have ‘trowsered’ the hard-earned savings of another decade.
1925		Wodehouse Carry on, Jeeves 132: I wrenched Uncle James’s card off a toy aeroplane, substituted my own, and trousered the squirt.
1946		S. Jackson Indiscreet Guide to Soho 54: Several dance band leaders trouser a fiver for every tune played.
1960		Wodehouse Jeeves in the Offing 166: The first thing he saw [...] was the speech. He trousered it.
1978		F. Norman Dead Butler Caper 49: He trousered the note and managed a smile.
1998		Guardian Sport 2 Oct. 16: Wrighty’s trousering a handy couple of long ’uns.
2000		P. Howard Miseducation of Ross O’Carroll-Kelly (2004) 83: I trouser the sponds.
2009		Eve. Standard 18 May 17/4: If the project goes ahead, Alsop will trouser millions in fees.
2019		P. Temple ‘High Art’ in The Red Hand 37: Make a few calls, trouser two grand.
2024		J. Meades Empty Wigs (t/s) 577: The dinari they trousered in a week was more than most people make in several lifetimes.

In phrases

trouser off (v.)

(Irish) to ejaculate.

1987

(con. 1920s) L. Redmond Emerald Square 294: My own opinion was that he [...] had ‘trousered off in his cambers’ before he got near it.