The term "3 legit" was created due to the absence of a word that captures the highest level of legitimacy in the English language. Since its introduction, the word has seen widespread usage, especially in the Northeast, with students of New York University being one of the earliest adopters of its usage.
Evolution: legit -> too legit -> 2 legit -> 3 legit
"Holy ****, that's 3 legit!!!"
"Kate Beckinsale just asked me to dinner."
"OMG WTFUX, THAT'S 3 LEGIT!!!"