The surname Bionaz is of clearly toponymic origin and is linked to the territory of the Aosta Valley. According to E. De Felice, it is a Valdostan surname formed from the place name Bionaz (AO), following the common pattern of identifying people by their place of provenance.

Along the same lines, E. Rossoni confirms this geographical origin, indicating that the surname is typically Valdostan, especially in the Aosta area, and that it derives directly from the locality of Bionaz. This agreement between authors reinforces the interpretation of a surname linked to a specific community of the Alpine arc.

Taken together, both perspectives agree in pointing to a strictly toponymic origin, with no evidence of anthroponymic or occupational derivations, which places Bionaz within the group of surnames that directly preserve the reference to their place of origin.