"...original ballad said to be from southern Germany, and much older." Since the German song was collected in 1843, the date of origin is problematical.

Archer Taylor, "The Themes Common to English and German Balladry, 1940, Modern Language Quarterly, 1:23-35, discusses the song, collected in Coblentz. Not seen.
This, and Wiora, cited above, may have some answers.