While the origins of the name Arthur are unclear, the name is thought to be of Celtic origin and means "bear". It is derived from Celtic elements artos, meaning "bear" combined with viros, meaning "man," or rigos, meaning "king". The name Arthur was most famously popularised by the legendary King Arthur, the mythical leader of the Britons and commander of the Knights of the Round Table. The name came into common use in England during the Middle Ages due to the popularity of the Arthurian tales and peaked in popularity during the 19th century.