12c., a merger of Old English ora "ore, unworked metal" (related to eorþe "earth," see earth; and cognate with Low German ur "iron-containing ore," Dutch oer, Old Norse aurr "gravel"); and Old English ar "brass, copper, bronze," from Proto-Germanic *ajiz- (cognates: Old Norse eir "brass, copper," German ehern "brazen," Gothic aiz "bronze"), from PIE root *aus- (2) "gold" (see aureate). The two words were not fully assimilated till 17c.; what emerged has the form of ar but the meaning of ora.