The phrase 'blue blood' originates from an old sentiment that aristocratic blood was blue. Normally used to describe royal family members.
Example in use: "I often remind my husband that I have blue blood flowing through my veins."
Interesting fact about Blue Blood
This phrase probably comes from the fact that at the time, in England, it was not posh to have a sun tan, since manual workers were always tanned from being outdoors all day, so those who stayed indoors had to be wealthy!
