Graffiti and graffito are from the Italian word graffiato ("scratched"). "Graffiti" is applied in art history to works of art produced by scratching a design into a surface.
Graffiti in Barcelona by Miss Van from Toulouse
A related term is "graffito," which involves scratching through one layer of pigment to reveal another beneath it. This technique was primarily used by potters who would glaze their wares and then scratch a design into it. In ancient times, graffiti was carved on walls with a sharp object, although sometimes chalk or coal were used. The Greek infinitive γράφειν - graphein - meaning "to write," is from the same root.