Why when a new Pope is elected?

Question

he changes his name, to say Paul, instead of using his own name? Thank you.

Answer 1

Just as someone getting confirmed in the Catholic church picks a new saint's name to add to their other names, a new pope can pick a saint's name or another pope's name as a way of showing their respect for that historical person, and if it's a saint, saying that it's a person they would try to emulate while they are pope.

Answer 2

Mostly custom.

No Pope is obligated to change his name. This is a pious tradition (not Sacred Tradition).

The practice arose when a pagan convert to Christianity became Pope and changed his name from Mercury (after the pagan Roman god) to John II in 533 C.E.

Until then, the Popes kept their original names, from Peter (#1) to Boniface II (#55).

Between John II (#56) and Sergius IV (#142) in 1009 C.E. only a few Popes changed their names.

But since Sergius IV, it has been common practice for all Popes to change their name when elected pontiff except Adrian VI and Marcellus II.

Pope Benedict XVI chose the name Benedict for several reasons. At his papal audience on April 27, 2005, he explained his motivations for adopting the name.

“I want to call myself Benedict XVI to bind myself to the venerated Pope Benedict XV, who guided the church in a troubled period because of the First World War. He was a courageous and authentic prophet of peace and worked with valiant courage first to prevent the drama of war and then to limit its nefarious consequences. In his footsteps, I want to place my ministry at the service of reconciliation and harmony among individuals and peoples, deeply convinced that the great good of peace is, first of all, a gift of God, a fragile and precious gift to invoke, safeguard and build day after day with the help of everyone.”

Benedict XVI also said he chose the name to evoke the spirit of Saint Benedict, the founder of Western monasticism whose influence helped spread Christianity over Europe.

“St. Benedict is very venerated in Germany, particularly in Bavaria, my homeland. He is a basic point of reference for the unity of Europe and a strong reminder of the undeniable Christian roots of its culture and civilization.”

http://www.usccb.org/comm/popebenedictxvi/namebenedict.shtml
http://www.newadvent.org/cathen/12260a.htm

With love in Christ.

Answer 3

He really wants to be called god. It's the closest the catholics will ever get.

Answer 4

"Regnal names" or "throne names" are common throughout history.