People commonly say that, but with WSL 1 it was technically quite correct: it’s a Windows Subsystem, for providing Linux. Linux Subsystem for Windows would arguably be slightly inaccurate. The name just feels so strange because Windows hasn’t had many such Subsystems (win32 has essentially been the only one this century).
Under WSL2, the WSL name is no longer technically accurate at all, but it’s what everyone knows it as, and the difference normally doesn’t matter, so they keep it.
I think of it as "Windows Subsystem for [running] Linux".
The architecture descends from the Windows NT architecture:
The user mode layer of Windows NT is made up of the "Environment subsystems", which run applications written for many different types of operating systems, and the "Integral subsystem", which operates system-specific functions on behalf of environment subsystems.
Though as other users pointed out, in WSL 2, the name is inaccurate.
There was a MS employee on twitter the other day (sorry, I forgot who) saying it was because there were legal issues with naming something with a title that has someone else's trademark as the first word.
That completely makes sense in my mind just because my favorite reddit app is called slide for reddit. I think reddit forced everyone to use x for Reddit in their name as opposed to Reddit X.
Reddit did exactly that, like five or six years ago. A bunch of apps had to change their names, which is how you end up with apps like "rif is fun for Reddit," where the first part stands for "Reddit is Fun."
