An acronym for people from the Chicago metro as mentioned in the above definitions, especially when visiting Wisconsin, that properly describes the attitude and character of those people.
If Chicago started with an "I", the rest of Illinios would have the same acronym for people from Chicago. The rest of Illinois views Chicagoans as a plague of locusts on good, honest, hard-working people from outside of the Chicago metro, who suck up all of their resources, right down to their souls, and then cop a FIB attitude towards them when they complain about it.
For an example of the attitude of a FIB, which is the main reason for the nickname, just read what the FIB wrote in definition number 10. This moron has the typical attitude of a FIB, that they are superior human beings to all others in the world, their percieved value of wealth makes them better human beings, and the rest of the world should be saying "thank you" and wiping their asses for gracing it with their presence and money. This guy is worst kind of FIB, and can keep his money in Chicago if that is going to be his attitude.