The surname Agrati is of clearly toponymic origin and is linked to localities in northern Italy. According to E. De Felice, it is a Lombard surname, especially Milanese, formed from the place names Agrate Brianza (province of Milan) and Agrate Conturbia (province of Novara).

Along the same lines, E. Rossoni confirms this interpretation, noting that the surname derives from these place names —Lombard in the first case and Piedmontese in the second— and that it originally indicated the place of provenance of the founder of the lineage.

Taken together, both interpretations agree in pointing to a precise geographical origin, where the surname Agrati identifies people coming from localities called Agrate, following a pattern very common in the formation of surnames in medieval Italy.