a word from German origin, originally used in a joke - now used to insult people commonly referred to as mentally retarded. The story behind is this: A desperate couple wants to have sex but has run out of condoms. Having thought about it again and again, they finally agree on using coffee filter paper instead. The woman gets pregnant and gives birth to a boy. Due to the filtering process within the sexual act, the boy when born is utterly dumb.
Hey man, you're a real Filter Tony.