In 1964, the famous boxer changed his name to Muhammad Ali as a result of converting to the Islamic religion. Muhammad stands for being praiseworthy, and Ali stands for the most high. Prior to the name change, he was Cassius Clay.
Muhammad Ali changing his name was controversial at the time because he told the press that his birth name was also the name of a white slave master. Reporters wanted to know if he would go through the process of changing his name legally, and Ali told them that he had no intentions of doing this because he rejected the thought that he needed permission to pick out a name for himself.