"Always thought that it was Scottish and Cowdenknowes,"
It is Scottish, it is rare to get it from a source singer and even rarer to get it from a singer from Northern Ireland
I think most of us were introduced to it by MacColl's singing _ I was anyway   
I used the spelling given in 'British Ballads from Maine' - I am aware that it is probably incorrect
The Maine collection includes many other obviously Scots ballads taken from Irish singers - the 'The Two Magicians' for instance
Jim