It does relate to the old border disputes between England & Scotland, where the Scot, Douglas, decided that and English hunting party, led by Percy was encroaching on Scottish lands. Huge battle ensues, and blood was spilled.

Then, the ballad writers (the equivalent of Hollywood) got hold of it, and details were embroidered as to the exploits and injuries and deaths of major characters, making the story more 'interesting', whether accurate or not.

It's only been recorded a few times, and the 'best' one I have heard is by Gordeanna McCulloch, whose voice is so high I can barely understand her.