There used to be an operating system called "V" that ran the "W window System".
en.wikipedia.org/wiki/V_(opera…
en.wikipedia.org/wiki/W_Window…
W was ported to #Unix at MIT and switched to an asynchronous protocol. It was renamed to "X".
XFree86 and Xorg are implementations of X version 11, or "X11".
If there would be an "X12", this is what it might look like:
In case you're curious about Wayland and not "Y", it's because it already exists:
