The Flatlanders are actually, Joe Ely, Butch Hancock and Jimmie Dale Gilmore
You're both wrong.
"Flatlanders" is the polite term Wisconsin residents use to describe visitors from Illinois.
FIB (or more commonly, FIBber) is the acronym of a less polite term. (Here's a hint to the full term: I stands for Illinois, B is a derogatory reference to one's parentage and I will leave the F to your imagination).