What is "riothamus"

Riothamus (also spelled Riutimus or Riotimus) was a Romano-British military leader, who was active circa AD 470. He fought against the Goths in alliance with the declining Roman Empire. He is called " King of the Britons" by the 6th-century historian Jordanes, but the extent of his realm is unclear. Riothamus is a Latinization of the Brythonic personal name *Rigotamos, meaning 'king-most', 'supreme king' or 'highest king'. Though it is still a matter of debate, several scholars consider his life to have been one of the possible sources for the King Arthur legend.