Elaine is an Old French spelling of Greek Helen (as in Helen of Troy).
"Elaine" is the name of numerous characters in the Arthurian Legends invented by the authors of the medieval French Arthurian Romances. Some notable examples include:
Elaine of Corbenic, also variantly known as Helaine, Helizabel, Heliabel, Amite, Perevida, or the Grail Maiden, the daughter of King Pelles, or alternately, The Fisher King, and the mother of that purest of knights, Sir Galahad. Elaine either falls in love with Sir Lancelot or else is put up to it by her father, but in any case by means of a magical enchantment appears to Lancelot as Guinevere to get him to sleep with her, and out of this paradoxically sinful union, conceives the saintly Galahad, who will ultimately be the only knight pure enough to find the Holy Grail.
Elaine of Astolat, also known as Elaine the Fair, first appearing in the Vulgate romance La Mort le Roi Artu (c. 1237) as a cursed maiden who dies of unrequited love for Sir Lancelot. Her dead body arrives in Camelot on a mystical barge, and Arthur orders her buried in a magnificent tomb. Elaine of Astolat, is now probably best known as the title character in Tennyson's poem The Lady of Shalott.
Elaine, or Blasine, the legitimate daughter of Igraine and Gorlois, and thus King Arthur's half-sister and full sister to Morgause and Morgan Le Fay. She is married to King Nentres of Garlot. Otherwise little is said of her.
Elaine, the daughter of King Pellinore who kills herself after the death of her lover, Sir Miles of the Laundes.
Elaine, Lancelot's mother and the wife of King Ban of Benwick according to the French tradition.
Elaine, Arthur's niece, who is fathered by either King Lot of Orkney or King Nentres, depending on the tale. She falls in love with Sir Percival in some versions.