Green’s Dictionary of Slang

1. (US) plain, simple, down-to-earth.

1951		Porter Ragged Roads 116: In plain old corn-bread language we would just call them [i.e. the obese] ‘hog fat’.
1971		R.D. Pharr S.R.O. (1998) 97: ‘I told the Sinman you talks all slurred like to get along with these here cornbread niggers we got, but you was born up North’.
2008		S. Bryan Moon North Carolina 192: She petted my arm, and said with a gravity that indicated that she was speaking the wisdom of the ages, ‘We’re cornbread people’.

2. (US black) conventional, ‘square’.

1957		H. Simmons Corner Boy 34: Performers [...] who belonged to the corn-bread crowd, but were considered good listening.
1962		(con. 1940s) H. Simmons Man Walking On Eggshells 155: He even made a couple of sets [...] at the Red Top, playing cornbread music for the boogie-woogie crowd.