I have 'Braes of Balquiddher' in "Songs of Scotland" edited by George Farquhar Graham in about 1850 ot so...he says it was written by Robet Tannahill, 'a Paisley weaver' 1744-1810...it gives a 'short' bio of Tannahill which claims that he was a well-to-do but morose person who committed suicide.