My colleague Barry put together these tasty clips from the 1980s ground-breaking scifi movie "Tron." Barry pulled out every use of the word "rez" in the film to explain why Global Kids named its new social network for virtual world educators "RezEd.org."
"Rez" in the Second Life context refers to creating objects in-world, i.e. to "rez a cube." Also waiting for textures and objects to load in your browser when you first coming in-world is often called "rezzing." In converse, to delete an object is to "de-rez" it. Torley Linden’s video clearly explains this use of the term.
RezEd is a cool site, btw. You should check it out, if you are interested in learning using virtual world technology.