The authors agree that this surname derives from an apocopated hypocoristic form (aphaeresis) of the name Michele. E. De Felice specifies that the base is the hypocoristic Chèle, documented in a Florentine register of 1308 —where the form "Chele filius Michelis" appears— and that both in Tuscany and in Puglia the name was already attested from the 12th century. He also notes that the variant Chelli refers more frequently to the hypocoristic Chèllo, derived in turn from Rustichèllo.

E. Rossoni broadens the origin, indicating that all the variants of the surname derive, directly or indirectly, from the aphaeresis of Michele or of its archaic form Michiello, and that its transformation into a surname is documented in San Miniato in a deed of 1336. The geographical distribution is wide: Cheli and Chelli extend throughout Tuscany and the Bologna area; Chellini appears in localities of the Florence and Siena areas and in Livorno; Chieli is concentrated in the Arezzo and Perugia areas; Chielli in the Bari and Taranto areas; Chiellini in the Pisa and Livorno areas; Chiellino in the Catanzaro, Crotone and Cosenza areas; and Chiello in the Caserta, Salerno, Foggia and Palermo areas.