The authors agree that this surname derives from the Germanic given name Kuonrat, composed of the roots kuon (or kuoni), "bold" or "daring", and rat (or radi), "counsel", with the general sense of "bold counsel". E. De Stefani notes that the surname is a derivative of the father's name that was continued without suffixes, and that its diffusion is due to the fame of several German kings who bore it between the years 811 (Conrad I) and 1237 (Conrad IV), until over time it became a surname.

A. Bongioanni highlights that the name is equivalent in meaning to the Greek Thrasybulus, and notes among its saints Saint Conrad of Piacenza (14th century, celebrated on 19 April) and Blessed Conrad of Molfetta (9 April). He also enumerates numerous derived forms according to the region: Corrado and Corradi in Liguria; Raddi, Radini and Radino; the Piedmontese Conrotto; Curetti in the Mondovì area; Curreno (documented as Conradengus or Currengus, of patronymic origin); Corrà in Trieste; Corrarini in the Veneto; Corridoni in the Marche; Ridoni and Currò in Trieste; Curotto in Liguria; and Corrao and Rao in southern Italy. In Venice and Friuli he also records Coradazzi, Corazza, Corazzi, Corazzin and Corretto.

De Stefani adds that the surname is distributed throughout Italy, with especially marked presence in Lombardy, Piedmont, Lazio, Campania, Calabria, Basilicata and Puglia, as well as in Trieste and in Tramonti di Mezzo. V. Blunda, for his part, treats it as a surname of Germanic root with rooting in Sicily, and notes that the variants Corrao, Currado and Currào reflect phonetic adaptations characteristic of southern Italian.