>>19749698mogging comes from "AMOG" meaning alpha male of group, aka the Chad in a group of mixed company who all the women want to fuck. If you are talking to some girls and Chad comes up and becomes the center of attention (often costing you the girl), you are said to have been "mogged."
Hence a girl with small tits is "mogged" by her large-chested friend in social interactions, who will presumably be the center of male attention.
