English form of the Greek ‘Ελενη (Helene), probably from Greek ‘ελενη (helene) "torch" or "corposant", or possibly related to σεληνη (selene) "moon". In Greek mythology Helen was the daughter of Zeus and Leda, whose kidnapping by Paris was the cause of the Trojan War. The name was also borne by the 4th-century Saint Helena, mother of the Roman emperor Constantine, who supposedly found the True Cross during a trip to Jerusalem.
The name was originally used among early Christians in honour of the saint, as opposed to the classical character. In England it was commonly spelled Ellen during the Middle Ages, and the spelling Helen was not regularly used until after the Renaissance. A famous bearer was Helen Keller (1880-1968), an American author and lecturer who was both blind and deaf.