When did the popes start using another name besides their own name?
Could the pope have chosen to continue using his name Joseph?
John II in 533 was the first one not to use his given name. His given name was Mercury which was also the name of a pagan god.
Haj
One of the early popes had the birthname Mercury (this was back when Roman polytheism was still around and his parents were traditionalists). He decided it wasn’t fitting to be named after a pagan diety when he was head of the Christian church so he renamed himself after one of his predecessors.
Some popes have decided to keep their birthnames; Pope Marcellus II was Marcello Cervini, Pope Adrian VI was Adrian Florensz Dedal, Pope John XXII was Jacques d’Euse, and Pope Julius II was Giuliano della Rovere.
Is the popes new name just an honorific, or does the pope actually change his name by deed poll (or whatever they have in the Vatican City)
“John” is “Jean” in French, and “Jacques” is “Jakob” (or “James”) in English.
Would not the first have been Simon?
“Jesus replied, “Blessed are you, Simon son of Jonah, … I tell you that you are Peter, and on this rock I will build my church,”