To track down names used during the pre-roman Ironage is difficult. Hardly any of them survive to the present day. Most of the male population changed their names to fit in with Roman society, and disappeared into the mass. Women, on the other hand, had no status under the Romans, so their names fare better!
To find male names, you have to look in Roman writings. Most name were translated into Latin, so the original language version is lost. The Romans also tended to put 'ix' on the end of a Celtic male name to show their status (not Roman), but that is a help to identify the Ironage people. Names with 'us' on the end are Romanised.

Take care, the names here are Ironage, not Irish or Welsh medieval names!