Sack tapping

It is also called "nut tag", "bag tag", "sack whack", "bell flicking" and "roshambo", the last name coming from an episode of South Park that featured the practice.

Sack tapping is a slang term for a game where a participant attacks, by slapping, tapping, punching, kicking, elbowing, twisting, or backhanding a victim's testicles. The term derived from 'sack', slang that refers to the scrotum, and the activity is a form of groin attack. This sociological manifestation of bullying can result in severe testicular injury that may require amputation as the only form of treatment.