E. Rossoni notes that this surname derives from patronymic forms in which the suffix -ato indicates "son of", referring to founders of the surname whose father was called Tonio, a form with the loss of the initial syllable of the name Antonio. The variant Toniatto is probably a transcription error of Toniato. Rossoni places the forms Toniati and Toniato as typically Venetan, especially in the Padua area and the bordering provinces of Vicenza, Treviso and Venice; the variant Toniatti, on the other hand, appears in the Sondrio area —particularly in Valfurva— and in zones of Trento and Bolzano.

F. De Laurentiis proposes, for his part, a derivation from Tognoli, a dialectal form likewise linked to the name Antonio, which points to a coinciding anthroponymic origin at its base, though through a different path of evolution.