Gotta be New Testament. When the Old Testament sealed, there still weren't Irish around. Unless those Irish were tribes (not Celtic; just nomadic tribes).
My FAC believed they (and the Scots, who came from Ireland - that part at least is true) were the lost tribe of Dan. On account of all the places with d_n in the name (Donegal, Dunedin etc). The French were Reuben, while England and America were Joseph's sons; so France is perennially pissed off with the Anglo nations, as they were the firstborn, dammit, but the Anglo-Americans got all the historical props.
One of the tribes was Belgium too. I don't remember which, which is just like Belgium.