It is also the name of two other minor characters who only appear while Arthur is searching for Dexter.
Dexter introduces himself to Arthur Mitchell as Kyle Butler at a church service. He continues to pretend it's his name in order to get close to Arthur.
After Dexter stops Arthur from killing Scott Smith, Arthur tries to find him. However, Arthur stumbles upon the real Kyle Butler, while trying to break into his house. Kyle threatens to call the police, which leaves Arthur no choice but to kill him in his home by bashing his head. Later, Dexter hears Kyle's name while with police at the crime scene.
Thinking that Arthur will continue to look for "Kyle Butler," Dexter subdues the next Kyle Butler on the phone book list so that he can get Arthur, when he comes searching for him. However, when Arthur breaks into Kyle's apartment, he sees Kyle's picture on a Christmas card and leaves, realizing that he is not the right person.