1850-55; < Italian, plural of graffito incised inscription or design, derivative with -ito-ite2 of graffiare to scratch, perhaps influenced by presumed Latin*graphīre to write; both probably derivative of Latingraphium stylus < Greekgrapheîon; cf. graphic, grapho-, graft1
In formal speech and writing graffiti takes a plural verb. In less formal contexts it is sometimes considered a mass noun and is used with a singular verb. The singular graffito is found mostly in archaeological and other technical writing.
1851, for ancient wall inscriptions found in the ruins of Pompeii, from It. graffiti, pl. of graffito "a scribbling," a dim. formation from graffio "a scratch or scribble," from graffiare "to scribble." Sense extended 1877 to recently made crude drawings and scribbling.