Webster's dates it to 1830.
OED quotations:
1830- "A name bestowed upon the Presbyterians in Fayetteville."
1893- "A name applied by the better class of people to the poorer inhabitants of the rural districts." A. Shands, "Some Peculiarities of Speech in Mississippi."
And many more.

Charmion, I would like to see the song. I remember it as a saying when comparisons were made between poor whites and Blacks. The poor whites often were in direr straits, in the minds of white southerners and southwesterners.