It is unknown whether Riothamus was a king in Britain or Armorica. Armorica was a Brittonic colony and Jordanes writes that Riothamus "crossed the ocean", so it is possible that both are correct. The name "Riothamus" is interpreted by Ashe and some other scholars as a title meaning "High King", though there is no evidence for such a title being used by ancient Britons or Gauls, and the formation of the name (noun/adjective + superlative -tamo- suffix) follows a pattern found in numerous other Brittonic and Gaulish personal names. Cognates of the name Riothamus survive in Old Welsh ("Riatav"/"Riadaf") and Old Breton ("Riatam"); all are derived from Common Brittonic "*Rigotamos", meaning "Most Kingly" or "Kingliest".