Expression used by Americans to refer to Englishmen. Dates back to at least the middle ages when the aristocracy rarely, if ever, went out of doors. The result was a transparent, alabaster complexion which made the veins beneath the skin appear prominent and blue. Example: Most Americans think the actor Christopher Plummer is a blue-blood when, in fact, he's a Canadian.
BLUE-BLOOD
Meaning of BLUE-BLOOD in English
Slang English vocab. Английский сленговый словарь. 2012