Very similar to trench foot caught by soldiers during world war I, trench cock is obtained after a long night of rough fucking in which both parties fall asleep while the male's one eyed battering ram remains inside the female's pork wallet. The excessive amount of moisture exposed to penis causes it to saturate and smolder causing the infamous trench cock. Extreme cases have resulted in the male genitalia sloughing (falling) off.
Friend #1: Hey bud how did last night go with that slut you scooped up from the titty club?
Friend #2: Aw man it was going great, I was really pounding that shit when we both passed out.
Friend #1: What is the big deal about that?
Friend #2: Well I fell asleep with my cock still inside her.
Friend #1: And?
Friend #2: Well I am worried I may have gotten trench cock and now my junk might fall off.