Of high or noble birth. The term is a translation of the Spanish sangre azul, which was applied to Spain’s pure-blooded aristocrats, meaning those whose ancestors had not intermarried with the Moors. Consequently they were fairly light-skinned and their veins showed bluer through the skin than those in Spaniards of mixed blood. The expression was used in England from the early nineteenth century, and was, like so many, satirized by W. S. Gilbert (Iolanthe, 1882, where Lord Tolloller is complaining that the fair maid Phyllis is not impressed by his title): “Blue blood! blue blood! When virtuous love is sought thy power is naught, though dating from the Flood, blue blood!”