The last pope before John Paul I to use a new papal name was Pope Lando in 913. They say he was also the last pope to use his given name as his papal name. [See comments–ed.] There has been no Pope Chewbacca.
On the radio I heard the morning DJs joke that the new pope could have chosen any name for his papacy, even Cletus. Little did they know that the third pope ever was Pope St. Cletus.