What's the etymology of the term "rez" in the Netrunner games?
It is short for "resolve", and derez is short for "deresolve". I have seen the terms several times in cyberpunk fiction; the earliest use I can find is Tron (1982).

Here are some quotes from IMDB. Note that the MCP uses the term "deresolution" when being formal, and the anthropomorphic programs use "de-rezzed" to mean the same thing.