Thanks Sedayne: your link has downloaded as 18 pages in Microsoft word. Will take some time to study properly but the reference to Tweed mill dams certainly points in a definite geographical direction.
Norman Kennedy's sleeve notes are:
'This wonderful ancient ballad (Child#10) is known far and wide - usually as Binnorie in Scotland but as The Two Sisiers in North America. The old singers I knew had different ways of singing the ballad - some with more verses than others. I frequently sing it at waulkings among weavers in America to shrink newly woven blanketing, so many people know it and happily join in the chorus lines'.