Green’s Dictionary of Slang

(Anglo-Irish) Mountjoy Prison, Dublin; also attrib.

c.1940–5		‘Myles na gCopaleen’ Best of Myles (1968) 150: justice (to Sergeant): This man is about twenty feet away from me yet I can get the smell of drink. Is he intoxicated? [...] For a man who has been in Mountjoy for over a week, you surprise me. defendant: Joy ale.
1955		J.P. Donleavy Ginger Man (1958) 182: I say, old boy, how would you like to spend Christmas in the ‘Joy’.
1966		P. Boyle At Night All Cats Are Grey 250: When he wasn’t in the Joy or the Glass-House or in Arbour Hill he was being kicked out of one job after another.
1994		(con. 1930s) K.C. Kearns Dublin Tenement Life 128: Now I done four days in the ‘Joy’ (Mountjoy) over the licence – I wouldn’t pay the five shillings for the licence.
1998		J. O’Connor Salesman 363: Then it was Spike Island. And then the Joy. You name a nick, I was there, man.
2005		P. Howard Curious Incident of the Dog in the Nightdress 270: The other 30 per cent haven’t been in the Joy yet.