Latinate name, first used by Shakespeare for the rich heiress wooed by the duke in Twelfth Night (1599). Shakespeare may have taken it as a feminine form of Oliver or he may have derived it from Latin oliva ‘olive’. In the 1970s it was particularly associated with the Australian pop singer and actress Olivia Newton-John (b. 1948). Since the 1990s it has been very popular throughout the English-speaking world.
Galician: Castilianized spelling of Valadares, a habitational name from various places in Galicia, so named from a derivative of valado ‘boundary wall’, ‘ditch’ (from Latin vallus, vallum ‘fence’, ‘barrier’, ‘bastion’).