https://en.wikipedia.org/wiki/Centrifugal_governor
edit: I once said this phrase at a work meeting and someone objected to my use of a crude term which I then explained much to everyone's surprise. They thought it had something to do with testicles.
The first attested use is from 1945, on the nose of a P-47 Thunderbolt flown by Captain Milton Thompson of the 509th Fighter Squadron. And his art was exactly what you'd expect: a charging bull with the words "balls out".
This is from the article, but governors also played a role in kicking off modern control theory! """ In 1868, James Clerk Maxwell studied when these oscillations grow or die away in his paper “On Governors”[https://www.damtp.cam.ac.uk/user/gold/pdfs/teaching/old_lite...]. This became one of the beginnings of modern control theory. """
The choice of wording makes me suspect that they intended both entendres. ;)
The one I like is why do we use birds to refer to female anatomy? I also heard something the other day and had an epiphany, but the sort you can't really tell anyone. "Oh... it means pouch that makes so much more sense, it's not a cat."
Going balls to the wall means pushing the throttle and mixture all the way in to the firewall/instrument panel for maximum power.
https://www.thedrive.com/news/the-phrase-balls-to-the-wall-c...