But I think it’s relevant to say that before writing Unix he was working on Multics for a long time already. Unix was a “simplified” version of it, if I remember well. So it didn’t “spring out of thin air.”
[1] SELinux is unmanageable; just turn it off if it gets in your way:
https://multicians.org/unix.html
"Brian Kernighan takes credit for the idea, but adds that 'no one can remember' the origin of the final spelling Unix."
https://en.wikipedia.org/wiki/Unix
Also note that Prof. Kernighan has written a historical memoir about Unix:
Right. Almost nothing does.
You see, it's https://en.m.wikipedia.org/wiki/Turtles_all_the_way_down