The authors agree that this surname has as its base the family name Cele or Celi, an aphaeretic hypocoristic —that is, an affectionate and diminutive form resulting from the dropping of the initial syllable— of Micele or Miceli, a variant of the personal name Michele, which later became a surname. In Sicily, according to E. Rossoni, Celi functioned as a habitual diminutive of Michele.

Rossoni adds a second hypothesis, valid especially in southern Italy, which proposes the derivation directly from the aphaeresis of the surname Miceli. He also mentions that at the beginning of the 17th century a certain Marcantonio Celi worked as a notary in L'Aquila.

E. De Felice notes that the surname is spread mainly in the south, and that some derived forms —such as Celín, Celoni, Celón, Celotto and Celussi— are found in the northeast of Italy, in the regions of Veneto, Friuli-Venezia Giulia and Trentino-Alto Adige. F. Miranda confirms this distribution and records among the variants: Cielo, Cieli, Celini, Celotti and Celozzi. Rossoni, for his part, locates the form Celi in the area of the Strait of Messina and in the area of confluence between the Marche, Abruzzo and Lazio, and the variant Celini in the Taranto area.