Seems like it stuck in the South, at least in Faulkner's days.

I think that Faulkner just knew the etymology of the word. (I could be wrong, just saying.)

Any specific difference between hominy and polenta as far as you know?

Yes. Polenta, at least post-New-World-discovery, is made from untreated, ground, dried corn (maize). Hominy is corn (maize) that has first been treated by soaking in lye-water (link).

Ceci n'est pas un seing.