Green’s Dictionary of Slang

(Irish) the real thing, the ultimate example.

1916		Joyce Portrait of the Artist as a Young Man 29: Stephen looked at the plump turkey which had lain, trussed and skewered, on the kitchen table. He knew that his father had paid a guinea for it in Dunn’s [...] he remembered the man’s voice when he had said: – Take that one sir. That’s the real Ally Daly.
1942		(con. 1890s) S. O’Casey Pictures in the Hallway 124: You’re a decent lad, a real decent lad, heart o’ th’ rowl, he said; th’ real Annie Daly, he said, one in a thousand.
1958		(con. 1940s) B. Behan Borstal Boy 94: When there’s one of them here among you, the real Ally Daly, the real goat’s genolickers.
1969		P. Boyle All Looks Yellow to the Jaundiced Eye 30: ‘You can’t whack it, Ma’am,’ he said. ‘The real Ally Dooley.’.
1981		(con. 1920s) P. Crosbie Your Dinner’s Poured Out! 219: It was the rale Ally Daly.
2008		in Munster Exp. 28 Nov. 🌐 By God Woman, You are the real ally daley, what an absolute dinger.