It'a a traditional desendent of a broadside ballad of about 1630, 'constant wife (also known as 'Locks and Bolts do hinder), ZN3202, in the broadside ballad index at www.erols.com/olsonw. It's obviously descended from some older, but unknown tale, poem, or song. There are several 17th century versions known, and are crossed referenced in the broadside ballad index. At the later Scottish "Earl Brand" it becomes a Child ballad.