Takes the form of "Well, it's not very good, but..." or the like.
Comes from the old southern tradition of playing down one's food cooked for friends or family. "The dough didn't rise how I was hoping..." etc.
"Ok." She said, "but just know I was up late last night and I don't think I'll be very good at the assignment today."
"Please don't southern-biscuit, Sarah." Replied her teacher. "I'm sure you'll do fine."