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 (very common in England, especially in the south Midlands, and in Wales) and German (especially northwestern Germany): patronymic from the personal name Adam. In the U.S. this form has absorbed many patronymics and other derivatives of Adam in languages other than English. (For forms, see Hanks and Hodges 1988.)