"The following verse of another once common song in the district around Auchterarder was wont to be sung to the of 'The Bonnie Hoose o' Airlie':
"Ye'll take the high road, an' I'll tak the low road, An' I'll be in Scotland afore ye; For it's me an' ma true love, we'll meet once more again On the bonnie, bonnie banks o' Loch Lomond."
The Dundee "Northern Warder" (Sept. 18, 1883) notes that the air of "Bonnie House o' Airly [sic]" was the tune used for "Flora's Lament" and provides the text.
It certainly looks like the lyricist of "Loch Lomond" took the chorus from "Flora's Lament" and wrote a new song around it.