name of an imaginary realm in "Las sergas de Esplandián" ("Exploits of Espladán"), a romance by Spanish writer Garci Ordóñez de Montalvo, published in 1510. It was a sequel to his "Amadis de Gaula," and was said to have been influential among Spanish explorers of the New World. It could have led them to misidentify Baja California as this mythical land and to mistake it for an island. The Amadis tales are the Iberian equivalent of the Arthurian romances; they are older than 1510 (traces of them have been found mid-14c.) and were wildly popular. That conquistadors and sailors would have known the story in all its imaginative detail is hardly surprising.
Amadis de Gaula ... set a fashion: all later Spanish writers of books of chivalry adopted the machinery of Amadis de Gaula. Later knights were not less brave (they could not be braver than) Amadis; heroines were not less lovely (they could not be lovelier) than Oriana; there was nothing for it but to make the dragons more appalling, the giants larger, the wizards craftier, the magic castles more inaccessible, the enchanted lakes deeper. Subsequent books of chivalry are simple variants of the types in Amadis de Gaula: Cervantes made his barber describe it as 'the best of all books of this kind.' This verdict is essentially just. Amadis de Gaula was read everywhere, especially in the French version of Herberay des Essarts. It was done into Hebrew during the sixteenth century, and attracted readers as different as St Ignatius of Loyola and Henry of Navarre. Its vogue perhaps somewhat exceeded its merit, but its merits are not inconsiderable. [James Fitzmaurice-Kelly, "Spanish Literature," 1922 edition]
Where Montalvo got the name and what it means, if anything, is a mystery. In reference to the native inhabitants, Californian is attested from 1785 as an adjective, 1789 as a noun. The element Californium (1950) was named in reference to University of California, where it was discovered.