Anglicised as "Arthur", the Latin is a Romanised form of the Celtic name based on the word "art" meaning "a bear". The famous Ulster king, Cormac Mac Airt, kidnapper of Deirdre and murderer of the Sons of Uisneach testifies to the age of the name in Ireland. It continues in use to the present day in both its original Irish form and the Anglicised form "Arthur".
Arturius