"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.
You can also increase speed by not using any propellers or moving parts. At supersonic speeds you capture the air, compress it into a chamber than hit it with a spark and blow the fucker up. That's how a ramjet engine works. China just made one that uses pulse like combustions in a engine that's only about a foot wide, and maybe 13 feet long. Speeds up to mach 4.. or 5000km/h (3100mph) at about 65,000 feet.
The Corsair had water injection as a WEP, I forget by what mechanism it worked but it could make that big ol' Pratt & Whitney eat its own guts for more horsepower.
Thanks, that's a lot more than my sketchy memory of what my dad told me (WWII pilot). Might not be where "under the wire" came from but it's fascinating.