Jack Balkin provides a bit of entertaining history on papal names and "the prophesies of St. Malachy, an Irish Bishop who lived in the twelfth century, and who is supposed to have prophesied all of the future popes."

Malachy's list offers prophetic mottos for 112 remaining popes. Each is supposed to describe some aspect of the pope's life, or, in the case of the earlier popes, a feature of his heraldic coat of arms.
[...]
The motto for the next pope, Ratzinger, now Benedict XVI, is de gloriae olivae, "[He] of the glory of the olive"...

One of several possible meanings for the "olive" reference is the olive branch as a sign of peace. Was the new Pope considering the prophecy when he chose "Benedict"? Was this a reference to the most recent Benedict, the fifteenth, who pushed for peace throughout World War I?

As Balkin notes, "Perhaps fittingly, Pope Benedict XVI has chosen pax or "peace" as his papal motto."