Sauron, of course, wasn't Sauron's original name. He was called Mairon the Admirable. Mairon was only given the name Sauron upon his defection to evil. The name Sauron was given in mockery of his previous name.
saura (Þ) adj. foul, evil-smelling, putrid
Sauro (Þ) masc. name Sauron (Þ), the Abhorred, name of a Maia, the second Dark Lord
Melkor, his master, was named Morgoth specifically by Fëanor. Who, exactly, renamed Mairon as Sauron (the Abhorred)?