Blue blood

The origin of this phrase is Spanish from The Middle Ages when Spain was embroiled with its wars against the invading Moors. The Moors occupied certain parts of Spain for hundreds of years and, whether consensual or not, the result was very often offspring of mixed blood. Spanish aristocratic families coined the phrase sangre azul “blue blood” to distinguish themselves from Spanish of mixed blood, pointing to the bluish tint of their veins on their light-coloured skin compared to the darker shades of Spanish people that had started to evolve. English borrowed the expression and Shakespeare uses it in Rape of Lucrece, line 1501. “Her blue blood changed to black in every vein.”