As a result of their obsessive interest in a specific subject, nerds are usually profoundly snobbish about their passions. Their accompagnying social impairment leads them to preach wide and far to everyone, inconsiderate of their feelings, about things they do not approve of.
As the term nerd is associated with being intelligent and having extensive knowledge of one or more fields, being labeled as a nerd is increasing i popularity. The term snerd serves to inform a nerd that he/she has crossed the line, even for a nerd.
"Jim, you are such a fucking snerd!"
dude 1: hey dude look at that kid over there in the tight red jeans waiting for the new harry potter movie.
dude 2: yea man what a snerd hahahah.