Green’s Dictionary of Slang

1. a prison.

1884		St James’s Gazette 4 Jan. 12: He preferred to go to choker [F&H].
1888		Cornishman 31 May 7/1: I want to keep out of ‘choker’ but how can I manage it?

2. (Irish) a cell for solitary confinement.

1888		Cornishman 14 June 7/3: He was summarily marched off to ‘choker’ for stealing food intended for Her Majesty’s pigs.
1997		Irish Times 18 Feb. n.p.: [At Spike Island prison] [...] there is what staff call a ‘cooler’ and prisoners the ‘choker’ [BS].