The Wikipedia article you posted says:

> The term "X-Windows" (in the manner of the subsequently released "Microsoft Windows") is not officially endorsed – with X Consortium release manager Matt Landau stating in 1993, "There is no such thing as 'X Windows' or 'X Window', despite the repeated misuse of the forms by the trade rags"[60] – though it has been in common informal use since early in the history of X[61] and has been used deliberately for provocative effect, for example in the Unix-Haters Handbook.[8]

I'd just like to interject for a moment. What you're referring to as Linux, is in fact, GNU/Linux, or as I've recently taken to calling it, GNU plus Linux. Linux is not an operating system unto itself, but rather another free component of a fully functioning GNU system made useful by the GNU corelibs, shell utilities and vital system components comprising a full OS as defined by POSIX. Many computer users run a modified version of the GNU system every day, without realizing it. Through a peculiar turn of events, the version of GNU which is widely used today is often called “Linux,” and many of its users are not aware that it is basically the GNU system, developed by the GNU Project. There really is a Linux, and these people are using it, but it is just a part of the system they use.

Linux is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Linux is normally used in combination with the GNU operating system: the whole system is basically GNU with Linux added, or GNU/Linux. All the so-called “Linux” distributions are really distributions of GNU/Linux.

Essentially all the distributions are GNU + Linux kernel + a whole bunch of other stuff that tend to have some common elements but vary by distribution. At which point we're into pedantry about what things are called.

You're right, and that's why I call it GNU/Linux. However, I don't run it. I use the world's best operating system, Windows 11 Pro for Arm.

And MANY people involved with it and Unix for a very long time routinely use the term, officially endorsed or not. Understandably because it is/was a windowing system and just saying X out of context isn't especially clear.