The term was devised by an American academic to refer to the graffiti found on toilet walls. Since biblical days, writing on a wall has been a way of making people sit up and pay attention. In 1635, Rembrandt painted a scene from the Book of Daniel, capturing a prophetic moment in ancient Babylonian history. King Belshazzar was tucking into a grand feast after having pillaged the Jewish temple in Jerusalem, when a disembodied finger appeared out of nowhere and wrote a message on the palace wall, spelling the kingdom's doom for his blasphemy against the Almighty.
Other ancient forms of graffiti can be found amid the remains of Pompeii, Italy (where the term originated). One inscription found in the preserved city warned of Celadus the Thracier, who 'made the girls moan'.
In 1992, a well-meaning youth group called Eclaireurs de France used their graffiti-scrubbing equipment to erase ancient paintings in the Meyrieres Cave in France, earning them the Ig Nobel Prize in archaeology.
When done without the property owner's consent, grafitti is considered vandalism. Nevertheless, different schools of graffiti styles and methodology have sprung up and spread all over the world. On the street, most urban youths can differentiate between a 'tag', a 'throw-up' and a 'piece'.
We've all stumbled across a graffito on a toilet wall at the local pub; we might even have contributed a verse or two to what has been affectionately known as 's**thouse poetry'. In fact, this form of graffiti had been catalogued and studied long before the invention of the spray can.
Between 1904 and 1914, Austrian folklorist F.S. Krauss published Anthropopytheia as 10 yearbooks. Within these volumes, lavatory graffiti is documented and discussed from a folklore point of view.