graffiti: [19] Although it denotes ‘writing’, graffiti has no etymological connection with Greek gráphein, source of English graphic. It comes from the plural of Italian graffito, a diminutive form of the noun graffio ‘scratching’. This was derived from the verb graffiare ‘scratch’, itself originally formed from graffio ‘hook’.
graffiti (n.)
1851, "ancient wall inscriptions found in the ruins of Pompeii," from Italian graffiti, plural of graffito "a scribbling," a diminutive formation from graffio "a scratch or scribble," from graffiare "to scribble," ultimately from Greek graphein "to scratch, draw, write" (see -graphy). They are found in many ancient places, but the habit was especially popular among the Romans. Sense extended 1877 to recently made crude drawings and scribbling in public places.