Apparently this statue was sculpted in the 15th century, back when people mostly couldn't read. The purpose of this statue was to show people what's wrong and forbidden (pleasing yourself in this case). The placement of Von Hochstaden's name is pure coincidence apparently. Also the town of cologne only learned about this obscenity when they saw a picture of it on the blog of a Hongkong tourist.
If I may add, I study history of art and apparently the church really wasn't that strict about rules at some point, bishops had wives and kids, they wasn't following their own rules, and everyone was pretty chilled about anything bottom-related. Back then a popular kids game consisted on (sit down for this) grabbing a friend, putting down your pants and farting on him. Obscene, lewd and poop related jokes were as present as anything else, because there was no real taboo - it was officially bad to do it, but hey, everyone was not Mr Perfect. So in a lot of European churches/cathedral etc these representations meant 'hey kiddos you're not supposed to do that' but it was just like seing for instance a guy eating cake, no taboo.
And sometimes they were only there for shit and giggles, in my town the cathedral has a sculpture of a guy with a bird up his ass :D
And sometimes they were only there for shit and giggles, in my town the cathedral has a sculpture of a guy with a bird up his ass :D