The word Smurf is used in Gaming Scene. The Word Smurf is taken from “The Smurfs” (original: Les Schtroumpfs). The connection for using it in the gaming context, is the defining characteristic of a Smurf. He is very little! Transferred to gaming, it describes the fact, that a experienced person is starting a game again from the scratch to level up just for fun. He will not put much effort in it but will slowly become a maximal level Character. In different gaming communities, there are different words for the same procedure. For example in the WOW community Twink got the same meaning as smurf.
I play with my Smurf, because i dont want to play with my main.