Man, I say this a lot and I know it comes across standoffish, but... US ethnic categorizations seem bonkers to me.

What does "half Jewish half Irish" even mean? Isn't that a Jewish person from Ireland? That would count as fully both things. What are the other two halves?

This is why I have to think about the immigration form for ten minutes each time I get through customs in the US, it's all "was any of your grandparents a smurf?" and "are you latino and/or lactose intolerant?" and stuff like that. It makes no sense.