MtheGM, I not only knew Robin but produced a couple of LPs with him and Jimmie, plusI solo recordings of Robin.
Robin, like Jimmie, was a Glasgow man and in those days, the songs were sung without any meaningful research. Robin was one of the finest singers I knew and you can take it from me I spent many a night with them both discussing Scottish songs. Robin's knowledge about Scottish literature then was lacking in any depth. Dominic Behan once chased him down the road, hitting him over the head with a copy of Burns's poetry, so incensed was Dominic at Robin's ignorance.
My degree in Scottish ethnology from Edinburgh University is a testament to the time and research I devoted to this subject.
I think you're reading too much into this song. One of the girl's boyfriends was killed at the fair and the other was drowned in the river.
You won't find any meaning of 'lour' to mean a fight but as it has nothing to do with the song it's irrelevant.