I think it basically means softWARES (WAREZ), but like many things to do with fringe society, they have to make it sound cool, like HACKERZ, and apparently the 'Z' makes it cool.
Warez is just wares witha "z" instead of an "s", and wares is just short for softwares. When you see short names that end with "z" like Appz, Gamez, and Warez, then it's pirated software.
Class rip means its a rip by a release group named CLASS. They deal with "rips" of the games. They release copies where you dont need to burn the game to a cd to play. And it usually takes up a lot less space. BUT, they usually have music/movies etc taken out of the game, but then come later in packs to download.