It was the name of the famous medieval legend, although historians dispute the existence of any King Arthur in British history.
Most historians concur that the myth is based on a number of leaders in England and France prior to the conquest which eventually became encapsulated in a number of translated texts.
King Arthur appeared in several books from around the 12th century with the famous image of Arthur pulling a sword out of a stone coming from Thomas Malory’s 15th century Le Morte d’Arthur.

Arthur was, therefore, a logical choice for the Wales’s second-born son, although in reality, the real meaning behind the choice might not be the one commonly understood.
The name was one of the middle names of King George VI, the father of Queen Elizabeth II and Louis’ great-great-grandfather.
This may have been the real reason underpinning the choice of middle name, a mark of respect to the late Queen’s father with whom she shared a close bond.