I was thinking of Sharp's English collections - except for the sea shanties, of course.

While most of the areas visited by Sharp were "settled" before 1800, movement into southwestern Virginia and Appalachia in general continued for a long time after that. I can't remember if Sharp got into the Georgia mountains at all, but they were wilderness til about 1825.

I'm not disputing your point, just saying that the appearance of a text in Sharp & Karpeles is not automatically a guarantee of pre-19th century origin.