In Starship's linked video, Ricky Skaggs says it's a public domain song, so unfortunately we'll likely never know who the true author was.

It's ironic in a way that Ricky Skaggs sang it in that video for Ralph Stanley, who wasn't feeling well at the time of that recording (1989). I was at Ricky Skaggs's concert in 2016 in Charlotte, NC on the day he found out Ralph passed... it was one of the most heartfelt and powerful concerts I've ever attended.