As I said before, Siul-Shule-- is old, but use of the word "Buttermilk" is not. Probably put in because some 20th century singer preferred it to "Younder" or "Portland" or whatever.
Oral or anecdotal tradition is just that. If the gap is large, it must be taken with a cellar of salt. If a song was popular, there is usually some evidence of it.