The authors agree that the surname derives from the name Ptolemaios through its Latin and Italian adaptations, though they differ in the weight they assign to each path of formation.

E. De Felice notes that the surname may reflect, especially in Tuscany and northern Italy, the aphaeretic hypocoristic of Bartolomeo —that is, the reduced form Tolomeo, with the loss of the initial syllable Bar-. However, in southern Italy, where the old Greek and Byzantine tradition persists, the base would be directly the Greek name Ptolemaios, also through its Latin adaptation Ptolemaeus. Related forms such as Tolomeo and Tolumello are documented in Calabria and Sicily; Tolomio in Veneto; and Tolomelli in Emilia-Romagna.

E. Rossoni places the focus exclusively on the loss of the initial syllable of the Latin name Bartolomeus as the origin of these forms, without contemplating the direct Greek path. He locates the surname Tolomei mainly in the Lucca area, with a secondary presence in the Venice area and in Lazio. He adds that Tolomio is concentrated in the Padua, Treviso and especially Venice areas, and considers that the variant Tolomi is probably a transcription error.