Any bruising that results from rough sex. E
sp if the bruising causes outsiders to believe that you are in an abusive relationship.
The term comes from the Twilight series. Specifically, the injuries Bell Swan-Cullen sustained during her honeymoon in Breaking Dawn.
Girl 1: Hey, what's up with that bruise on your arm? Did someone hit you?
Girl 2: Nah, it's just a Swan mark
Girl 1: Good on ya!