Using “Balls” as a Representation of Courage, Strength, etc.

I’ve seen a lot of feminists (on this blog and otherwise) explain why they dislike the use of the word "pussy" to mean weak, because it equates weakness or inability with having a vagina. Of course I agree that it’s disgustingly misogynistic and needs to stop. But it got me thinking about testicles being used as a symbol of bravery or strength — i.e., when someone accomplishes some feat, or does something badass, or shows some display or bravery, it’s said that, "So-and-so is ballsy!" "Man, so-and-so’s got kahones." "That takes serious balls," etc.

So, vagina=weak, fragile, and incapable while testicles=strong, brave, and defiant. This pattern sure sounds familiar, don’t it?