Arthur is the name of the central character in Arthurian legend, a 6th-century king of the Britons who resisted Saxon invaders. He may or may not have been based on a real person. He first appears in Welsh poems and chronicles (perhaps briefly in the 7th-century poem Y Gododdin and more definitively and extensively in the 9th-century History of the Britons [1]). However, his character was not developed until the chronicles of the 12th-century Geoffrey of Monmouth [2]. His tales were later taken up and expanded by French and English writers.
The name came into general use in England in the Middle Ages due to the prevalence of Arthurian romances, and it enjoyed a surge of popularity in the 19th century. Famous bearers include German philosopher Arthur Schopenhauer (1788-1860), mystery author and Sherlock Holmes creator Arthur Conan Doyle (1859-1930), and science-fiction author Arthur C. Clarke (1917-2008).
Already an uncommon masculine name, it slowly grew in popularity for American girls beginning in 1978 after the start of the sitcom WKRP in Cincinnati, which featured a character with this name. Though it remained more common as a feminine name, it got a boost for boys in 1994 from another television character on the drama Party of Five. In the United Kingdom and Australia it has always been more popular for boys.
Although this is a grammatically masculine adjective in French, it is given to girls as well as boys in Britain and the Netherlands. In America it is more exclusively masculine. It is not commonly used as a name in France itself.
Because Elijah was a popular figure in medieval tales, and because his name was borne by a few early saints (who are usually known by the Latin form Elias), the name came into general use during the Middle Ages. In medieval England it was usually spelled Elis. It died out there by the 16th century, but it was revived by the Puritans in the form Elijah after the Protestant Reformation. The name became popular during the 1990s and 2000s, especially in America where it broke into the top ten in 2016.