EWTN Catholic Q&A
Pope's name
Question from Marie Bartolome on 04-20-2005:

How long did it take Cardinal Ratzinger to decide on a name? Do you think some of the cardinal-electors already have a name in mind before entering the Conclave, anticipating that they just might be elected pope? Thank you :)

Answer by Matthew Bunson on 04-21-2005:

It is impossible to know if Cardinal Electors enter with some idea of a name they might choose. The decision in taking a name is made immediately after accepting election by the College; the new pope is asked by what name he wishes to be called.