As Alan Of Australia pointed to it's first (English) appearance in print was 1658, it's belive to be of Norwegian/Scandinavian extraction & exists as a folktale, ballad & as a children's piece. It's been collected in the US, Scandinavian countries, the Balkans, Great Britain, Ireland & throughout Western Eurpoe. So it's quite possible that it's been floating around for quite some time prior to it's appearance as a broadside. Bronson suggests that the versions with the rare refrain 'swan swims' are associated with Celtic communities. Although the older versions were longer, they carried a message for the younger listeners of yore. Folktales & ballads were used to help guide the child of yesteryear into adulthood, the more it was heard the less chance of forgetting the lesson, the longer the lesson, the more to be absorbed. Child & Bronson both have this but see Paul G Brewster 'The Two Sisters' Folklore Fellows Communication #147, Helsinki, 1953 for a main study. Barry