The "NS" prefix was introduced with OpenStep in 1994[1]. OpenStep was a collaboration between NeXT and Sun[2]. So the S in "NS" referring to Sun is certainly plausible!
[1] https://developer.apple.com/library/archive/documentation/Co...
[1] https://developer.apple.com/library/archive/documentation/Co...
> Totally wrong. The NS prefix predated Sun signing on to implement the OpenStep spec by quite a bit. It was either NS for “NeXTStep” or “New System”. None of us can remember which, though, but definitely not NeXT-Sun.