The authors agree that the surname derives from the given name Lancellotto (also Lancilotto, Lancialotto), the Italian adaptation of the French Lancelot, the name of the celebrated knight of the Round Table, lover of Queen Guinevere, spread in Italy from the 13th century onwards through the chivalric romances of the Breton cycle.

E. De Felice notes that the variants with an initial A- —such as Ancelotti and the like— were formed by deglutination of the initial l-, mistakenly read as the definite article. E. Rossoni further proposes a more detailed etymology: the French lancelot would derive from ancel, itself from the Latin ancilla ("maidservant"), so that ancelot would be a diminutive with the sense of "serving knight", which, when articulated as l'ancelot, gave rise to Lancelot.

Rossoni documents a broad family of variants. Lancellotti is fairly common, with a presence in the Brescia area, in that of Modena, in Rome, between the Naples and Salerno areas, and in Oppido Lucano, in the Potenza area. Lancelotti is typical of Gardone Val Trompia, in the Brescia area. Lancerotto is proper to Veneto, with cores in Campolongo Maggiore (Venice area), Verona, Montagnana (Padua area) and Lonigo (Vicenza area).

Rossoni also records southern forms: Lanzillotta appears in the Apulia area —in Taranto, Martina Franca, Bitetto, Polignano a Mare, Castellana Grotte and Conversano— and in the Cosenza area. Lancellotta has a core in Fornelli (Isernia area) and another in Belvedere Marittimo (Cosenza area). Lanzellotta is very rare and is found in Fasano, in the Brindisi area.