Zombieland

The scene where Columbus says, "It had to be a clown. No, it had to be a clown, and it had to be Wichita for me to finally understand that some rules are made to be broken." (Rule #17: Don't be a hero.) Columbus is faced with his biggest fear, which stands between him and Wichita. Not only is Wichita the girl he desires, but she has become an integral part of the "cool, functional family" he has longed to be a member of. Although he created this list of rules to stay alive, before meeting the other characters, how alive was he? He was a loner with IBS, pride and dignity were long gone, and he avoided people. The road trip gave him a chance to connect with people and to find what he always wanted, a girl to love and a functional family. But, in order to keep these things, he's going to have to break old habits, face his fears, and break his own rules. At that point in his life, it was time for him to either nut up or shut up.

Question: What was the purpose of using hometown nicknames?