"Wabbish country"?

I've been reading the Alvin Maker series by Orson Scott Card, and he keeps referring to a region of the US as "Wabbish country". Any clue where he means? I mean, New England's a real place in our reality, and it's not too hard to figure out where he means by "Appalacia", but "Wabbish"? I'm guessing the upper-Midwest, but if anyone knows better, let me know.