Analysis of information sources in references of the Wikipedia article "MacOS" in Indonesian language version.
Of course X ("ex") does mean 10, but anyone who used to poke around on Unix systems will know that in those days anything Unix had an X ("ex") in it, and OS Ten is written OS X ("ex") in honour of the fact that it is based on UNIX, unlike its predecessors. So, hey, you can say it any way you want; me, I'm showing my age and sticking with X (ex).
Of course X ("ex") does mean 10, but anyone who used to poke around on Unix systems will know that in those days anything Unix had an X ("ex") in it, and OS Ten is written OS X ("ex") in honour of the fact that it is based on UNIX, unlike its predecessors. So, hey, you can say it any way you want; me, I'm showing my age and sticking with X (ex).