In the course of the 16-century Italian language controversy (questione della lingua) one of the recurrent topics was the origin and development of Italian. In the XVth century it was common to regard it as a mixed, “bastard” language, the result of Germanic conquests and subsequent language contacts. In the 16th century value judgments gave way to native language apology, to attempts at drawing parallels between Latin and Italian language systems. Thus, in the “Cesano”, a treatise by Claudio Tolomei, one can find ‒ alongside with the défense et illustration of Italian ‒ a number of original ideas on history of language. Tolomei describes the main phonetic changes from Latin to Italian and tries to account for some deviations from these rules.