Do Popes HAVE to Change Their Names?

That was a question on the excellent "Ask a Franciscan" site recently. The answer is no, they don't:

"According to J.N.D. Kelly’s The Oxford Dictionary of the Popes (Oxford University Press), the first man to change his name on being elected pope was John II in 533."

Why did he change his name? Because his real first name was Mercury, the Roman/pagan god of commerce.

Although "Pope Mercury" sounds pretty cool...