By now, you should know there are all kinds of Jews out there.
Polish Jews, Spanish Jews, Black Jews, You-name-it-they-exist Jews. Heck, we even knew an Eskimo Jew at one point (no, JONJ searchers, not Sarah Palin). So no one should be surprised by the existence of Irish Jews. But, boy, they're tough to find.
Perhaps it is because, in the Catholic vs. Protestant world of Ireland, being Jewish is like voting Nader. It's a valid choice, we suppose, but it's nothing that the rest of the country will understand, let alone embrace.
Or maybe it's Irish cuisine. Having recently visited, we can't exactly describe the Irish diet as Jew-friendly. Oh, the usual lambs and steaks and salmons are fine enough. But for some reason everything has bacon in it. Breakfast, lunch, dinner, dessert? Bacon, bacon, bacon, bacon. We're pretty sure we were offered bacon tea at one point. Not exactly an easy place to keep kosher.
So it makes sense that while Daniel Day-Lewis is both Jewish and Irish, it is only by descent on both sides (Jewish mother. Born and raised in England.) The cultures are simply too incompatible to be on any closer terms.
It's too bad. With both cultures' love of corned beef, we could have made one heck of a sandwich.