Well, I heard about this stuff when I red an introductory book on UNIX.
The meaning of the name is clear: the word 'UNIX' was protected by an ugly copyright, thou these guys maked a joke bt naming it like this
After a while (more precisely three year after that) I had in my hand a book on TCP/IP programming. I had been searching for a long time a book on this topic, so I opened it and I realized that I was going to do a great mistake: it was written for Mt Xinu.
The worst thing was that the primitives were different than the standard ones and the programming itself was very complicated.