I was just looking through the “urban dictionary” and looked up fr00b.
Here was what I found.
fr00b come from the internet game runescape. It was invented when one of the game moderators , Mod Mark, and the best player of the game , Zezima, were fooling around with ways to make fun of people, thus fr00b was born!
pmg die u h4x0r fr00b!
Source: gbuster4, Oct 7, 2004