The authors agree that this surname derives from the given name Saul, which transmits the name of the first king of Israel through Latin and biblical Greek Saul, an adaptation of the Hebrew Šā'ūl. The meaning attributed is "asked for or implored from God," in reference to a much-awaited child, or else "offered to God." The name was used during the Middle Ages also in non-Jewish spheres.

E. Rossoni notes that all the variants derive directly, or through dialect forms, from the Jewish name Saul or from the Latin name Saulus, and recalls that Paul of Tarsus was called Saulus before his conversion. Rossoni documents a wide geographic dispersion of the variants: Saule in Trieste; Sauli in Trieste, Rome and the L'Aquila area; Saulini in Rome and Bellegra; Saulino in Rome, Isernia and the Naples area; Saulle between the Caserta, Naples and Salerno areas, and also in the Bari area; Saulli in Rome and Rieti; Saullo in Naples, the Cosenza area and Alcamo in the Trapani area; and Saulo in Rome and Cetraro, in the Cosenza area.

E. De Felice points out that the form Saul has a greater frequency in Genoa, while Saule or Sauli are recorded in Trieste and Tuscany.