Once upon a time in Utrecht (the Netherlands), Moskou the famous white cat of an infamous Berlinian soap star escaped the safety of her home and was lost for days. When Moskou finally walked back in all dazed and confused, she appeared to have been run over by a truck with her white belly being all black with filth. In fact, Moskou had been brutally assaulted and impregnated by a neighbourhood tom*cat. Nowadays, all around the Netherlands and Germany, when someone speaks about “iemand een zwart buikje geven” (Dutch) or “giving someone a black belly” it expresses he or she is in the process of having ‘rather fierce sexual intercourse’ with that particular individual.
Giving someone a black belly (zwart buikje geven). (its all about the giving!) Iemand een zwart buikje geven. (Dutch)
Some guy: "He bro...I'll call you later...I'm giving her a black belly right now"
Other guy: "Genau!"
Some girl: "Damn, that guy sure gave me a black belly last night!"
Other girl: "Oh he gave you a black belly? Genau!"
Other guy: "Genau!, I'll give you both a black belly"