I finally got hold of the article referred to in the notes to the DT version of this. As I understand it, it argues that the basic source from which all current versions of this come is a broadsheet (probably "The Mountains High", of which several early 19th c. versions are known). The "supernatural" bit, suggesting vampires, werewolves or whatever, may come from verses written by the Irish Poet Joseph Campbell at the beginning of the 20th cent. Given that Bram Stoker was Irish, this may even be right! The idea was suggested by an informant of Hughes who said that "Reynardine" was the name of a "faery" which changed into a fox.

Not sure I believe this, yet...

Regards