Next up: Referer https://en.wikipedia.org/wiki/HTTP_referer#Etymology

I was an engineer at MS in the 90s. We've been using the term "setup" incorrectly since the beginning of time. It was "setup.exe", not "set up.exe" for an obvious reason.

You are conflating grammar with canonical usage. Should people use the correct form? Sure. Does it matter in the least? No.