Malcolm (or better yet, Arnie who first asked the question),

The research is yours now.

Find the earliest versions of the song in which the fox is chased by the hounds, even if it is or isn't named Reynard.

Find the earliest occurance of "Jubal" and "Joyful" in the song.

Find British and American versions. I saw plenty of information about the American Civil War General, and several other 19th Century American folks named "Jubal."

For extra credit, find French versions, the older the better. Reynard is a French name--perhaps there is something to be seen there. What adjectives are used to describe the dogs? If it did, when did this song cross the channel?

If the term appears in American or Appalachian versions but not in British (and/or French) versions, then there is a link to consider. If it is in older incidences of the British version, then I think you need to consider the Old Testament meaning.

SRS