If it wasn't for Burns' collecting and adapting of old songs many would have simply disappeared.

As well as his original work, he adapted many others from older traditional songs and 'improved' them on his terms - we can't tell if for the better or not.

The dates given by Rory earlier for similar songs are just an indication of the date they were first published, rather than proving a specific date & establishing the songs' provenance. Burns' songs like this one are probably an amalgamation of much older songs & impossible to date!

Or maybe there was ONE song actually composed c400 years away which went in different directions, but we will never know - that's the essence of traditional music, surely?
.... and yes, I've never heard it sung better than by Heather Heywood