Short form of Alessandra, the Italian form of Alexandra. A major influence in establishing this as a common given name in the English-speaking world was George Meredith's novel Sandra Belloni (1886), originally published as Emilia in England (1864); the heroine, Emilia Sandra Belloni, is a beautiful, passionate young singer.
English and Scottish: patronymic from the personal name John. As an American family name, Johnson has absorbed patronymics and many other derivatives of this name in continental European languages. (For forms, see Hanks and Hodges 1988.)