A lampoon or satire posted in a public place.
Derived from an early 1500s Roman statue named Pasquino. Upon this statue rapscallions (Italian rapscallions, now that I think of it … I feel either a rap or another Rocky sequel coming on …) took to posting anti-church screeds. High-minded graffiti.
One might mistakenly equate Pasquino with Momus, the Greek god of ridicule and blame. But Pasquino was no mythical figure; he was evidently just a statue minding his own business, used to malicious effect.