Jax Pavan was one of the 582,797,754 Human males named Jax Pavan on Coruscant. He was the 666th Jax Pavan to be registered on the planet. This was not just coincidence: he waited in front of the registration office until Jax Pavan 665 had been registered and then went to in to claim the number 666.
This turned out to be a bad idea because it so happened that Pulpitine randomly pulled the number 666 out of a bantha head and decided to use it as the target of a Great Number Purge that would help boost the image of the Galactic Religion. The Number Purge turned out Great, pulling in a record number of converts, but it was kinda bad for Jax Pavan 666, who got pwned by a local chapter of Pulpitine's zealots as well as Jax Pavan 667.