Interesting. My family roots in the South go back to the revolutionary days, and I have never heard the phrase (at least that I recall). I have a feeling that might be more a mountain southern saying. There can be vast differences in colloquialisms in different regions. I know in the coastal region of North Carolina, I’d often hear the phrase, “I ain’t studdin’ that!” quite often. It just means a person isn’t buying into someone’s crap usually, or they’re not getting duped or doing something they think is stupid. Anyway, I’ve never heard that expression in any other area.