in the unix o.s. (and unix based spinoffs), you have several standard directories, like DEV, BIN, and of course, USR. the 'yoozer' is a friendlier form (because most newbies find UNIX quite a hostile environment) and it can be used as a nick. (warning, nick is already taken, guess what, by ME. thank you.) Example: Yoozer is a looser! (about the most stupid form of insult that you can get on IRC. it means less tight.)
YOOZER
Meaning of YOOZER in English
Slang English vocab. Английский сленговый словарь. 2012