I've gone back and read the songs that have the phrase in it, and it looks to me like you're exactly right, Me.

I've never heard the expression myself, but if you've lived there and heard it, that's good evidence.

For example:

Turn your lamp down low
Turn your lamp down low
Turn your lamp down low
I beg you all night long, baby,
please don't go.

I am reminded of pop and country songs that take a phrase and use it over and over until it begins to seem more important than it really is. Remember Barry Manilow's "Even Now" ?

(Isn't it irritating how everybody from Anglia to Oz thinks they know all about the south based on movies and TV?)