Green’s Dictionary of Slang

Irish stew adj.

1. true; esp. in the phr. below.

1969		S.T. Kendall Up the Frog.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1992		R. Puxley Cockney Rabbit.
2001		M. Coles Bible in Cockney 33: I want you to come back with your youngest brother so I’ll know that what you’ve been telling me is Irish.
2002		M. Coles More Bible in Cockney 15: This agreement would finally all come to be Irish stew when Jesus Christ came along.

2. blue.

1992

R. Puxley Cockney Rabbit.

In phrases

too Irish (stew) (adj.) (also too bloody Irish (stew))

too true.

1930		(con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier 172: Too Bloody Irish! — Of course.
1937		J. Curtis You’re in the Racket, Too 243: ‘Anybody playing cards?’ ‘Too bloody Irish. There’s a nice little school in there.’.
1960		J. Franklyn Dict. of Rhy. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl. 39: too Irish stew. Too true.