Nennius, or Nemnivus, is either of two shadowy personages traditionally associated with the history of Wales. The better known of the two is Nennius, the student of Elvodugus. Elvodugus is commonly identified with the bishop Elfoddw of Gwynedd, who convinced the rest of the Welsh portion of Celtic Christianity to celebrate Easter on the same date as the other Catholics in Britain in 768, … Wikipedia
The definitive Wikipedia entry for Nennius. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Nennius