BLUE BLOOD

Translated from the old Spanish phrase "Sangre Azul", blue blood 
derives from the Medieval belief in Europe (among other places) that the blood of the royalty and nobility was blue; since the royal family and aristocrats were wealthy and powerful enough to pay commoners to labor in the fields for them, their skin was translucent and pale enough for their blue veins to stand out.

Old school slang for common folks back in medieval times. Those of low class work in hard labor (agricultural) and spending majority of the time being exposed to the sun; so they tan. Where as the high class folks do nothing, but stay inside their homes; getting paler. So pale that their skin become--as some say like alabaster, that you can see their blue veins through their skin. 
Thus the word "Blue Blood".

It also refers to old money families:

 families that have been aristocrats for many generations.
Comes from the medieval belief that aristocratic blood was blue.

Usually used talking about novelty and royal family members.


Royal Prince & Ms. De.