The word graffiti was actually
coined by historians excavating the ruins of Pompeii. So the practice certainly predates Gypsies in Wales; probably predates the Romans.
That being said, I'd love to learn more about Welsh Gypsy graffiti.
Irrelevant, but entertaining, examples of graffiti scrawled on walls in Pompeii:
(on the wall of a bar/brothel) Weep, you girls. My penis has given you up. Now it penetrates men’s behinds. Goodbye, wondrous femininity!
(in a house, below a drawing of a man with a large nose) Amplicatus, I know that Icarus is buggering you. Salvius wrote this.
(in the basilica) Let everyone one in love come and see. I want to break Venus’ ribs with clubs and cripple the goddess’ loins. If she can strike through my soft chest, then why can’t I smash her head with a club?
(Bar of Athictus; right of the door) I screwed the barmaid
(gladiator barracks) On April 19th, I made bread
Source
