Green’s Dictionary of Slang

jay! excl.

Jesus!

1922		Joyce Ulysses 12: O, jay, there’s no milk.
1954		B. Kiely Honey Seems Bitter 33: Here, try some Paddy, for jay’s sake.
1961		T. Murphy Whistle in the Dark Act I: Aw, jay, sham, don’t take it too serious.
1985		T. Murphy Conversations on a Homecoming (1986) 15: Aw Jay, that Galway race week!
1997		C. McPherson The Weir 14: Jays, four or five in anyway.