The act of runt shunting dates back to the medieval era. This was commonly defined as one's fist penetrating one other's/their own anal cavity. After this act was completed, the fister traditionally licked their hand, and/or offered it to their partner.
"Hey bitch, shunt my runt or i'll shunt yours!"
"I got the best runt shunt last night, it was Fred's turn to do the licking!"
"That was some good runt shunting, shall you lick or shall I?"