These words and notes are from Andy M. Stewart's CD Live Wizards: "Easily traceable back to the early seventeenth century where it appears in a small collection as The Lovely Northerne Lass. Allan Ramsay also published a version in his Tea Table Miscellany, during the 1720s. It is a moving tale of love, banishment and exile, supported by a very beautiful melody. Cowdenknowes is in Berwickshire, near to the village of Earlston, a place much associated with the 13th century poet and prophet, Thomas The Rhymer. I got this song years ago, from my friend and neighbour, Archie Fisher."
There is also a Child Ballad of this name with quite different word, though credited to the same source, The Lovely Northerne Lass. It may be found here.
The song and dance tunes differ slightly. Further, the song really needs to be much slower than the tune as played for dancing.