In Ovid’s account, Medusa was already named Medusa before she became a Gorgon. Ovid describes her as a beautiful mortal woman whose hair was later transformed into snakes.
The transformation story appears in Metamorphoses. Ovid says that Neptune, the Roman equivalent of Poseidon, assaulted Medusa in Minerva’s temple. Minerva, the Roman equivalent of Athena, then changed Medusa’s hair into snakes and made her face so terrible that anyone who looked at it would be turned to stone.
This version differs from earlier Greek traditions, in which Medusa is generally presented as one of the monstrous Gorgon sisters rather than as a formerly ordinary woman. The familiar story of Medusa’s beauty and punishment became especially influential in Roman and later European literature.
The question concerns her name, not a separate pre-Gorgon identity. Ovid does not give her another personal name before the transformation; she remains Medusa throughout the episode.