Loch Lomond

Folk musicians always insist that the meaning of the chorus comes from an ancient belief that Scots had that if ye died abroad, your spirit would find its way back to Scotland underground. Many cultures have this idea - notably there are varieties of Judaism that teach this about return to the Holy Land after death. So the man about to be executed reassures his fellow that all will be well in its own way. "I'll be in Scotland before ye."

The singers and poets and romantics are all quite sure. I have heard it told live a few times, and nodded wisely, as one of the clever ones who already knew that. I looked at a dozen versions on YouTube and the comment sections always put this in right off. They get the part about the Jacobite rebellions and the executions right, but this particular bit of folklore only comes in much later.  It's not likely to be true.  So many things about poems, songs, and rhymes that I have wanted to be true!

Tell you what.  You have to acknowledge the lack of evidence when the song isn't actually playing.  But when you are listening to it, you are allowed to believe.