History
Pope St. Gregory I was the first pope to use this title to refer to the office of the Pope. Some of his sucessors used the phrase off and on for the several hundred years, but it was not regularly used until the 9th century. Other civil rulers at times used this title as well, but after the 12th century it came to be used exclusively by the Pope.
In the years following the Second Vatican Council, Popes have used Servus Servorum Dei in making their office a simpler and less regal office. Pope Paul VI stopped using the Papal Tiara, and neither of his successors have ever worn the tiara. Both John Paul I and John Paul II had dispensed with the Papal Coronation ceremony, instead opting for a simple innaugration ceremony. Also, both men had dispensed with using the royal we in speech, and instead opted for the singular I.
