Mose Rager who was a mentor for Merle Travis had a daughter well 3 actually. One of them told me that Merle Learned that song from Mose Rager's brother Lyman. Lyman was in jail in Russellville Kentucky and learned it from an inmate. The name of the inmate has been lost but that is the story that has circulated around here in western Kentucky about the way Merle learned that song.
cya
JT