at my school last year there was a random kid who came in every bathroom (even the girls bathrooms) and no one ever caught them. so one of my friends coined the nickname "cum culprit" and sometimes id walk in and see a puddle of semen on the floor and say "ah fk the cum culprit strikes again"
TL;DR: someone came in my school's bathrooms last year and so we called them the "cum culprit"