A. Bongioanni notes that this surname derives from a Latin given name belonging to the gens Iulia, whose ancestry the poets of Antiquity traced back to Iulus or Ascanius, son of Aeneas. He proposes two possible etymologies: the expression caeso matris ventre, alluding to the birth by caesarean section, and the term caesaries, which means "head of hair". In both cases, the common root would be caed, from the verb caedere, "to cut". Bongioanni also mentions the existence of the name Caeso in Latin onomastics.

E. Rossoni broadens this perspective and notes that the various variants of the surname derive, directly or through affectionate forms, from the Latin cognomen Caesar, the name of the most famous leader of ancient Rome, which came to become a universal synonym of the term "emperor", as demonstrated by the Germanic Kaiser or the Russian Tsar, both derived from that name. Rossoni specifies that Cesare is distributed throughout Italy with greater concentration in Campania; Cesari predominates in the centre of the country and in Emilia-Romagna; Cesarini is located in the strip of the Marche, Umbria and Lazio; Cesaris appears in Lombardy; Cesaro and Cesarò in Veneto and Sicily respectively; while De Cesare, Di Cesare and De Cesari are concentrated mainly in southern Italy and in Lazio.