See the thread started as a sequel to the one in MMario's link above. Unfortunately, people immediately started to repeat the same misapprehensions already gone through in the original discussion, but some of these were cleared up eventually, and set of a Gaelic verses was posted. Not the "Gaelic original" of Roberton's lyric, of course, because there wasn't one, but another song sung to a variant of the same tune:

Mingulay Boat Song again