That's fascinating, Ebbie.   It seems clear the fiddler had heard both the words and the tune to the Bob Wills hit---no doubt he plays the tune all the time. But hadn't heard the words--(which as noted above were not in Bob's original hit version, but added later)-- for quite a while.   If you try, it's not hard to fit your fiddler's words into the Bob Wills "Maiden's Prayer" tune--which, as noted, he didn't write but adapted.    You do have to be careful where the accents fall in order to fit the fiddler's words to the tune.    Not having for a long time heard the words sometimes sung to this tune --since it's overwhelmingly done as an instrumental-- the fiddler made up his own words, with snatches of the earlier lyrics included.

Perfect "folk process".