We've heard that corn snakes were named for one of two reasons:
1.) Their rich colors sort of resemble the multi-colored kernels of Indian corn being grown by the Cherokees and other Indian tribes of the southeastern U.S.
2.) These snakes frequented the corn storage structures of the Indians (and the pioneers who came later) because of the rodent harvest that could be counted on proliferating there.
Which is more correct? We don't know - what's the difference? The name stuck!