VATICAN CITY — What’s in a name? A lot if you are the next pope.

Every time a new pontiff is chosen in a conclave, a senior cardinal goes up to him and asks: “And by what name do want to be called?”

The question is popped immediately, while all electors are still locked in the Sistine Chapel. So the winner had better have done his homework and already picked a name.

Shortly after, the senior cardinal reads out the pontifical name in Latin from the main balcony of St. Peter’s Basilica as part of the “Habemus Papam” — “We have a pope” — formula that proclaims the election of a new pope.

“The name the new pope chooses tells a lot about the thrust of his papacy,” said Ambrogio Piazzoni, a church historian and vice-prefect of the Vatican library.

Benedict XVI, the German Joseph Ratzinger who stunned the world last month by announcing his retirement, told pilgrims at his first public audience in 2005 that he had chosen the name in order to be guided by the early 20th-century Pope Benedict XV.

“In his footsteps I place my ministry, in the service of reconciliation and harmony between peoples,” said Benedict. The earlier Benedict, pope from 1914-22, led the church through the turbulent years of World War I and devoted much of his papacy to healing the rifts the war had created in Europe.

Ratzinger, who focused on Europe’s Christian heritage throughout his papacy, said he also drew inspiration from the 6th-century St. Benedict, founder of Western monasticism and considered responsible for helping to spread Christianity throughout Europe. One of Benedict XVI’s main priorities was trying to revive the faith in Europe.

Other popes in recent times have also looked to previous popes for inspiration.

In 1978, John Paul II kept the name of his immediate predecessor, John Paul I, out of deference to the earlier pope’s short-lived papacy. John Paul I — who took the first double name in history — was found dead in his bed in the papal apartments, after only 33 days as pontiff.

The Polish John Paul II, born with the name Karol Wojtyla, had also reportedly considered Stanislaw, out of respect for the patron saint of his native Poland.

Until the first millennium, popes were called by their first names, except for the 6th-century Roman Mercurious, who having been named by his parents after a pagan god, decided the name would not be appropriate for a pope. He chose the name of John II.

Speaking of Johns, Giuseppe Roncalli in 1958 became John XXIII because John the Baptist was the name of the parish church in the small town of Sotto il Monte in northern Italy where he was baptized.

Over the 2,000 year history of the church the most popular name is John followed by Gregory and Benedict. Pius was the most popular choice in the past century, picked by three popes. Another famous Pius was the 19th-century Pius IX, who holds the record as the longest reigning pope — almost 32 years.

So what is the new pope’s choice likely to be?

“It all depends on what message he wants to give out from the very first day,” Piazzoni said.