Why are blue bloods called blue bloods?

Answer 1

i am not shure but i think it is a slang name for the aristocracy or enny form of royalty. meening that thay are different . but most of all i as said beleve it was used as an inflamitiry remark and name.

If you are talking about the book Blue Bloods by Melissa De La Cruz

They are called Blue Bloods because there blood is blue

Blue blood is black blood (1100-1848) by egmond codfried can be read in Google and explains how brown and black complexioned Europeans became a nobility.

The part above was written by someone else but I wrote the paragraph below.

Well I'm pretty sure they say this because back in the day (I know that doesn't sound very professional or whatever), the wealthy/royal people did not do work in the sun where you would get tan, so they stayed pale and you could see their veins which were blue, so they called them blue bloods, whereas tanned slves, servants, farmers and just workers in general had tanner skin so you could not see their veins easily.