Why does the new pope change his name?

In many cultures, a change of name indicates a change in status or stage of life; in the Hebrew Scripture, for example, Abram and Sarai became Abraham and Sarah when God established his covenant (Gen 17). The papal tradition of taking a new name fits into this kind of ritual, but it is not directly related to it. The historical truth is far less prosaic. When a man named Mercury was elected pope in 533, he didn’t think it was a good idea for the bishop of Rome to share a name with a pagan Roman god, so he became John 11(533-35). Most, though not all, of the following popes continued the tradition of taking a new name to symbolize the new office so that within a few centuries it was common to do so. The last man to keep his own name was Marcello Cervini, who became Marcellus 11(1555).