According to Kevin Smith and Jason Mewes the origin is this: When Jason was younger, about 14, he used the "nee"-expression as a means of countering a statement just made, as in "I'm gonna fuck your mom tonight - nee". The "nee"-expression then grew and grew, but always refering to the canellation of "charge" in a statement. Thus, snoogans means to not do anything. Just the same as Wayne's world's "not!"-expression. Of course the snoogans works excellent as a stand alone-expression, but the "true" ethymology is the one stated above.
I could say, "Kage, you're a fucking faggot." He could get pissed off, then I just say, "Snoogans, dude!" You could also combine it in the sentence, if you don't want the pissed off reaction. You could instead say, "Kage, you're a fucking faggot... snoogans." It's definately a stoner thing.
The all-encompassing word that adapts to the current situation and describes the satisfying experience that cannot be accurately and extensively described by any other word or combination of words.
Note: Used frequently by the fictional (yet so real) characters, Jay and Silent Bob (Well not Bob as much as Jay, because he is the silent one.)