This is a chorus variant quoted in a February 1876 newspaper, where it has pretty much morphed, and can be fitted to the tune we all know. The song as we know it, really takes off in the 1880's-90's, when it can suddenly be found mentioned in theatre performances and as a 'parlour' song.

You'll take the high road, and I'll take the low road. And I'll be in Scotland before ye'. And It's I will meet my true love. My gallant, pretty boy. On the bonnie, bonnie banks of Loch Lomond.