Actually, it's a reference to inbred people from Wilmington, IL. Though being that Alabama is in the South and most ignorant people think inbreeding is a southern only thing, I can see how some could think that.
Wilmington became famous for being a stop on U.S. Route 66, which followed the route of modern-day Illinois Route 53. A notable attraction for travelers along this route is the hammers or yellow hammers that live in brodies woods they once worked on the railroad using yellow hammers and set up residency in Wilmington. They bred within the family and became mutant from insest.
We call people from Wilmington Illinois Yellowhammers, because at one time the hillbillies there were inbreeding. When I asked a chick where she was from, and she said Wilmington. I asked does she have any bruncles (brother+uncle)
if you say hes my brother/uncle and you are from Willmington Illinois. You ARE a yellowhammer......
If you say Hi Bruncle Tom, and are from Wilmington Illinois, you ARE a yellowhammer
If you look at your teen daughter and think shes do-able, and you are from Wilmington Il, you ARE a yellowhammer
(if you are from elsewhere, you should be hung from a tree, including Wilmington Illinois)
Inbred white trash. From the civil war term given to confederate soldiers from Alabama, whose state bird is the yellowhammer, a yellow-plumed woodpecker.