What's an Irish song?

I think there's a good chance that whatever song topped the poll wouldn't actually be Irish anyway.

For example - "I'll take you home again Kathleen" started as Austrian; "Wild Rover" is English (Norfolk) in origin; "Willie McBride" is Australian by an English emigrant. And then there's all those Tin Pan Alley American Irish songs like "When Irish eyes are smiling" or "MacNamara's band"...