Singing Together books sometimes named their immediate source, generally commercial published collections which themselves were not always particularly accurate.   You could always get in touch with John Adams himself and ask if he knows any more about the song.  He's currently the director of The Village Music Project at the University of Salford; contact details may be found at their website:  The Village Music Project.  It might also be worth posting a question at the uk.music.folk newsgroup.

Malcolm