Blue Blood

How did the term "Blue Blood" come about?

 

From Quora:

 Our family is Spanish and Italian and has studied this very subject for over a century now. The term definitely comes from the "sangre azul" phrase used by the Spanish after the Moor invasion of southern Spain, starting in the 700's. The royal nobles of Spain fled to the north and regrouped with several others in order to later fight off the Moors. The royals hated the Moors so much that they went out of their way to keep out of the sunlight and keep any trace of dark skin off of them. It wasn't so much that the Spanish were racist against what we call "blacks" nowadays or in the manner of how we perceive racism due to the American Civil War. It just so happen to be that the Africans (later called Moors) were dark skinned - something which the Spanish came to loathe after the invasion. They made it a point to work and live mostly in the dark, via candlelight or indirect light. With less sunlight, the veins did appear more blue through the pale skin, something which the other European nobles noted and were impressed by - hence coining the term "blue blood" as a literal translation from the Spanish "sangre azul." The silver theory is definitely something that has come up and has been discussed but has never been studied enough (in a clinical manner in regards to this subject) to say if, indeed, it caused it. Though, it is extremely probable and very likely because the Spanish were very fond of silver and did use it daily which would absolutely cause an ionic transference of sorts. Today, we simply translate "blue bloods" to royalty or "old money" as well as nobility. The Spanish were just extreme when it came to this area of history.