Comes from the combination of the words "ratchet", "pack", "dart" (being slang for cigarettes) and "gang".
Does not refer to just anyone that smokes cigarettes.
Every highschool has a ratchpack dartgang. Simply look to the smoker's corner for the dirtier looking kids who are always trying to bum smokes off of each other.
Andrew: That's just the ratchpack dartgang.