Don’t forget the PSX, which was originally used by the emulation scene to refer to the first Playstation. Then came Sony with an actual PSX which was a reworked PS2 with DVR capabilities that looked like a hi-fi component.
And the PS/1, which was a line of IBM PCs for the home (contemporary with the PS/2, and predecessor to the Aptiva range).
Or the PSOne, which was a cost-reduced late model PlayStation (1) :-)
I believe PSX was originally originally used by Sony as a codename for the PlayStation; not sure whether it was referred to as such externally by them. I think I remember gaming magazines at the time before the PS1s release referring to it as the PSX but am not certain.
It was referred to as PSX by pretty much everyone until the launch of the DVR, y eah.