Blue Blood

The phrase translates the Spanish "sangre azul," used by aristocratic families of Castile to claim their lineage was pure, untouched by intermarriage with the Moorish or Jewish populations of medieval Spain. The reasoning was as much visual as genealogical: aristocrats who stayed indoors and avoided outdoor labour kept pale skin, through which their veins appeared more visibly blue than the sun-darkened skin of labourers, and this was read as a mark of untainted, high-status ancestry. The concept was referenced generally in English by 1809, and a specific early example appears in Maria Edgeworth's 1834 novel Helen, describing a Spanish character "of the sangre azul, the blue blood." Within a few decades the phrase had been adopted for aristocrats of any nationality.