Pope
Popes are elected by Cardinals of the Catholic Church. Once they are elected they hold the position until they die or resign. Usually they do not resign, though; Pope Benedict XVI is the only Pope to resign in the last 500 years.  A newly elected Pope chooses a regnal name.  Everyone is told this new name when the Habemus Papam is read out. The current pope (Francis) was called Jorge Bergoglio before he became a pope.