Why is a beautiful blonde called a “blonde bombshell”?

The expression “blonde bombshell,” often used to describe a dynam-
ic and sexy woman with blonde hair, came from a 1933 movie star-
ring Jean Harlow. Hollywood first titled the film Bombshell, but
because it sounded like a war film, the British changed the title to
Blonde Bombshell. It originally referred only to the platinum-haired
Miss Harlow, but has come to mean any gorgeous woman of the
blonde persuasion.