It's not a new term, and it exists because there are unique practical engineering problems associated with high mach numbers so having a term for this regime is useful even if the distinction seems arbitrary from a pure theoretically perspective.
Sure, but "hyper"? Is there any reason other than that it sounds cooler than "super"?
What are we going to do when we hit mach 11, start talking about "hyperhypersonic"? "superhypersonic"?
It's a distinct regime, so useful to give it a distinc name. Super and hyper are roughly synonyms, but super was already taken.
There was also some precedence from wave research back in 1938 which suggested hypersonic and ultrasonic for high frequency waves[1].
At this point it's a well-established term, with 60 years of history[2].
[1]: https://www.ias.ac.in/public/Volumes/seca/007/03/0163-0176.p...
[2]: https://secwww.jhuapl.edu/techdigest/Content/techdigest/pdf/...
> Super and hyper are roughly synonyms
Perhaps you're right in terms of how they're leveraged in today's society. I'll drop my pedantry.
They roughly have the same meaning in the languages they were borrowed from, Latin[1] and Greek[2] respectively.
Yeah it's random, but established at this point. The radio bands aren't much better[3] with their Very High Frequency (VHF), Ultra High Frequency (UHF) and Super High Frequency (SHF) and Extremely High Frequency (EHF).
[1]: https://www.etymonline.com/word/super-
The term has been in use since the 1940s, pretty much as soon as it was sensible to think about making something that can go that fast. Does your modern perception of "hyper" being a cool word reflect how the word was perceived 80 years ago, or does your perception of the word being cool come from the way the word has since been used to describe such extreme things?
Maybe it was considered cool back then, but I wouldn't be sure of that. Maybe it was just an obscure latin term nerds used. I guess you could search comic book archives for clues. In any case, really fast things are cool, but only figuratively speaking.