N00b and nub are corruptions of “noob”, itself a corruption of “newb”, short for “newbie”. “Newbie” was in use at least as far back as the BBS era of the 1980s and early 1990s, where it referred to a user who was new to BBSs. It was less of an insult and more friendly than “noob”, which was popularized by Counterstrike players in a context where a poor player can ruin the game for others.
Newbie itself is modern slang, where according to Wikipedia it referred to new soldiers in Vietnam. The word’s origin before this is unclear, but it appears to be a word created to turn the adjective “new” into a noun, perhaps as a diminutive (Barbara -> Barbie, for example).
Informant & Context:
My informant is a commenter on the website Stack Exchange, who goes by the username Joe Dovakhiin, a popular message board website in the online gaming community. The comment was in response to a forum question about the origins of the word Noob. I believe the comment was legitimized by the more than twelve thousand thumbs ups it received by other forum users.
This is one of the most classic or conventional gaming insults in my opinion. It is a phrase that has continued to be used throughout my lifetime, and has a life span almost as large as the video game industry itself. This phrase is especially interested because it has maintained popularity in the entire gaming community whereas other phrases have gone in and out of style like fads.