Nah, I wasn't suggesting it was just Catholics got shot in times of trouble in Scotland, far from it.
But that line in Danny Boyabout saying an Ave rather implies it's Catholics involved. I thought I'd stick that in, in case anybody thought that fact might mean that the song had to be set in Ireland. Of course it doesn't, since there were always parts of the Highlands and Islands which stayed as Catholic as most parts of Ireland.
The Scots came from Ireland in late Roman times, and pushed the Picts (and the Romans) around, and the word itself is just another word for Irish I believe (would that be in Pictish?). But then were a whole bunch of other ones came across from the European mainland later, and somehow the Northern half of the Kingdom of Northumbria ended up as part of Scotland (with the Southern half becoming Geordies and suchlike).
The Scots are as mixed up "racially" as the English or the Irish - and all the better for it. And so is the music, thank God.