The authors agree that the surname derives from the medieval Latin name Bonus Senior (also documented as Bonussenior or Bonsenior), meaning "good lord". E. De Felice notes that this name is documented from the 10th century in Latinized forms, and that its use as an appellative and nickname was formed from bòn and signore.

De Felice adds that the surname is found sporadically throughout Italy, although it is frequent mainly in Sicily. He also highlights the abbreviated variant Bónsi, of predominantly Tuscan use, whose origin as an aphaeretic hypocoristic of Bonsignore is documented in a text in the vernacular of Florence around the year 1300, where one and the same person appears named indistinctly as Bonsignore and as Bonsi.

F. Miranda specifies that in Sicily, in the Catania area, the dialectal word bbonzignuri is equivalent to "monsignor" or "bishop", which reinforces the semantic link of the surname with a figure of authority or moral recognition. Miranda also mentions a documentary testimony in the Diplomatic Code of medieval Lombardy, with a text of 1115 in Milan, a fact confirmed by G. P. Holmes.