Why doss 'having balls' mean that you're brave and being a 'pussy' meaning you're scared? I mean if you hit a woman in the fetus they're fine they go through that every month, but if you hit a man in the testicles, they'll be rolling on the floor.
In this day and age, it's stupid to say something like that while addressing humans, because we aren't so primitive any more, but we used to be. That's why people said/say it. That's the answer to the question in your status. :w