I can't quite tell if you're being cheeky
> we don’t have a word for ... the ... distribution
> Until we have a ... word for the ... shell
distribution/distro and shell are exactly the words we have for these things
But OS sounds more impressive/important, so it's a lot more prevalent.
Microsoft hasn't really used that nomenclature since NT took over all their operating systems. Windows shell+kernel = OS. MacOS = shell+kernel = OS.
It's really the unix/linux world that stuck hard with these being separate things.