Does anyone know where the term dumb blonde came from and what reason a certain group uses it for?

Question

When the blonde hair is the epitome of the white race. Why not the dumb black haired person. This would include many races.

Answer 1

jealousy, darlin'

Answer 2

I don't know where it comes from, but if you met my son's blond girlfriend, you'd know why it's used. She is blond to the bone!