E. Rossoni sets out a possible double origin for this surname: on the one hand, a toponymic derivation from localities called Grotti —such as the one in the Perugia area— or similar, such as Montegrotto in the Padua area; on the other, a nickname-based origin from the dialect term groto ("pelican"). Rossoni documents the presence of the surname in Emilia-Romagna, with cores in Ferrara, Fanano (Modena area), Ravenna, Cesena, Sogliano al Rubicone and Rimini, as well as Bologna; and in Tuscany, in Arezzo, Foiano della Chiana, Camaiore (Lucca area) and Florence.

F. De Laurentiis proposes instead a directly lexical origin: the surname would derive from the Italian noun grotta, which designates both a natural cavity in limestone rock formed by the action of water and a cellar used as a larder or tavern. In this latter sense, according to De Laurentiis, Grotti would be the equivalent of "innkeeper" or oste. This etymon would also explain the existence of related forms such as Grotta, Grotte, Grotto and Grottino, all of them found in different areas of Italy.

The variant Grotto, according to Rossoni, is characteristic of Veneto, with a presence concentrated in the Vicenza area —in localities such as Schio, Thiene, Vicenza and others— and a lesser presence in the Rovigo, Venice and Treviso areas.