I believe, there was a real king Arthur but that wasn't his real name. There have been many articles on the internet and in books stating that king Arthur may actually have been king Owain Ddantgwyn,king of Powys and Gwynedd. 'Arthur' was the name used as a battle name meaning 'the bear', coined from Brythonic Celtic word 'Arth', and the Latin word 'Ursus' - both meaning 'bear' - thereby 'Arthursus' and later being shortened to 'Arthur'.