According to tradition, brown-haired Allan in the song is Allan of Kingsburgh, who became famous as the husband of Flora MacDonald. He was wrestling one day with Martin of Bealach, and Martin managed to put MacDonald down on his back. Sometime later some of the MacDonalds met a group of the Martins in an inn, and a fight broke out as described in the song.
'Songs Remembered in Exile' (J. L. Campbell) song 16
'Gesto Collection' (K. N. MacDonald) appendix p. 16