Similar to the nickname from old school. Frank the dank is usually a nickname given to someone who can smoke large amounts of weed. Frank the Dank is ONLY a nickname for true stoners. Instead of running naked in the street, someone referred to as Frank the Dank is probably giggling on a couch eating cheese puffs.
Dude 1: man how are you still awake?
Dude 2: I don't know I guess thats why they call me Frank the Dank