You will hear Apollo astronauts occasionally say "all balls" or "five balls." After performing maneuvers, they would check their trajectory by taking fixes on stars using the telescope/sextant, this data would be fed into the guidance computer, which would compute their deviation from their intended course. If they were perfectly on their intended course, it would display a variation of 00000. "All balls." Perfectly accurate.

I can Accept that

Interesting. Similarly, balls out has nothing to do with testicles

Oh shit sam o nella was right

"Just under the wire" has a similar aviation lineage. According to my dad some WWII fighter planes had a wire attached across the throttle lever slot to mark the point that was considered "full throttle". The wire was breakable, so a pilot in a desperate situation could push the throttle farther forward if necessary, but I think there was a danger of blowing up the engine. So being just under the wire meant not quite past that point.

Going "balls out" refers to governors on steam engines which used centrifugal force on a pair of balls to regulate the speed of the engine. At full speed the balls were out at the maximum.

Another fun phrase with similar etymology is "pulling out all the stops". It comes from church organs, where the stops are all of the levers that can change the timbre

Kind of like 'having one's balls in a vice'. It actually refers to the old days when ball bearings were made by hand. It was tedious work and the pressure to make ball bearings for the burgeoning industrial revolution was intense. They were cut out of metal and then polished smooth, secured in a vice. Hence, 'having your balls in a vice' meant being under intense pressure.

So is the term "grounded" and I genuinely wonder what parents used to say to their misbehaved children before airplane terminology was commonplace.

Not to be confused of course with "balls deep", which is exactly what it sounds like