Does the pope choose his own name or is it given to him? Why does it change?
The pope picks his own name. Although all of the popes since the Middle Ages have done so, it is not required to change your name. The first pope to change his name was John II in 533. His given name was Mercury, the name of a pagan god and he felt that his was not an appropriate name for the head of the church and he changed it. The last pope to keep his given name as pope was Marcellus II in 1555. Pope John Paul I was the first to choose two names. Until the election of Pope Francis in 2013, the last pope to choose a new, unused name was Pope Lando in 913.
When a pope chooses a new name, it might indicate his hopes for his reign, or tell us about his view of spirituality; it might also reflect continuity with a predecessor. In the early thirteenth century St. Francis of Assisi had a vision in which Jesus commanded him, “Repair my house, which as you see is falling into ruin.” In choosing St. Francis as his namesake, Pope Francis was pointing to a beloved saint who embraced radical simplicity, poverty, and care for the poor. As Pope Francis himself put it, “Oh, how I would like a church which is poor and for the poor!”