No, it's in regards to a mechanical governor known as a fly
ball.
It was a common method for governing the speed of steam powered devices. Two balls spin around a rod, when the centripetal force is great enough they spin all the way out towards the walls. I.e. "balls out", or "balls to the wall"
i have heard this - but i call bullshit.
it’s possible a non-pilot said it first.
But colloquialisms don’t catch on by governing steam powered devices.
They catch on by people wanting to talk like dudes that shoot nazis out of the sky.
Also my great uncle flew a P-38 in WWII and he used this term all the time.
Which is why i say it.
(p-38 cockpit.) 
