The authors agree that this surname derives from the Latin adjective carus, documented from the 8th century in Latinised forms such as Carus, Carellus, Caruccius, Carocius and Carullus, meaning "who is loved" or "who is much cherished". Its origin is linked to affectionate names and nicknames of the medieval period.

E. De Felice notes that the surname is spread mainly in southern Italy, where the patronymic and matronymic forms with De or Di are characteristic, the forms with Lo and La, and the compounds Carillo, Caricchio, Carullo and Carone. More scattered, it also appears in central Italy, in Tuscany and in Emilia-Romagna, especially in variants such as Cari, Caretti and Carini. This last form, in Sicily, reflects on the other hand the place name Carini, in the province of Palermo.

E. Rossoni adds that the base form Caro appears in a scattered way throughout Italy, without a defined regional concentration. He notes as a prominent figure the writer Annibal Caro, born in Civitanova Marche in 1507, famous for his translation of the Aeneid. The variant Carotti presents specific areas in the Cremona, Ancona, Florence, Grosseto, Terni, Rome and Rieti areas; the form Carotto, on the other hand, would be practically unique and probably the result of transcription errors of Carotti.