Made me delve a bit, the logical conclusion i came to:
it seems to be evolved from
https://en.wikipedia.org/wiki/PSX_(digital_video_recorder)
to https://m.emuparadise.me/Sony_Playstation_Emulators/Windows/PCSX/18
to
https://en.wikipedia.org/wiki/PCSX-Reloaded
and https://en.wikipedia.org/wiki/PCSX2
There is no mention on their page about it though. https://rpcs3.net/about
So an initial word play on PC and PS merged into PCS later added reloaded?
shot in the dark, because I've made that mistake before, if you got dyndns setup, it needs to be from the server not the router for ipv6 to work.