Several other sets of words, both Scottish and (later) Irish, are in other threads on this song (see links above). It has long been used as an all-purpose song of parting; as I've mentioned before ('origins' thread, with abc notation) the tune appeared in Gow's Repository of the Dance Music of Scotland, II, c.1802, p 76, with the comment 'This Tune is played at the Conclusion of every convivial Dancing meeting throughout Scotland.'

No particular reason to think that references to death or the army were ever intended, though of course the song in most of its forms is sufficiently general to be interpreted in that way if it suits the situation.