“Meatspace” was a response to “cyberspace”. If I think about it (and I make no claims to veracity here other than gut feel), I can’t think of anyone who’d use “meatspace” in earnest except those who spend too long in the alternative; but then again I also can’t think of anyone who’d use “cyberspace” in earnest except those who understand close to nothing about it. So they’re opposites but originate from the same place.

Anyway, Merriam-Webster claims the terms were introduced fairly close to each other, only about a decade apart, in the 80’s (cyber) and 90’s (meat).

https://www.merriam-webster.com/wordplay/what-is-meatspace