I tried to post an answer yesterday but it got chewed up somewhere in the system......
Mary Brooksbank was some feisty woman: political activist, yes definitely! Led the women of Dundee jute mills on strike for better pay, joined the Communist party and got imprisoned several times for her activities. She is commemorated by a blue plaque on the Dundee Women's Trail, which is a recommended route for anyone visiting Dundee.
See: Mary Brooksbank
By the way, there's a really nice more recent version of the song recorded by Ewan McLennan