The authors agree that this surname has a toponymic or architectural origin related to the concept of "solarium". E. De Felice proposes that it derives from a series of place names in northern Italy —Solaro, Solara, Solero, Soliera, Solieri, Solarolo— all of them linked to the late and medieval Latin solarius, meaning "field or land exposed to the sun", or to constructions such as casa solaria or castellum solarium, referring to buildings with an upper floor or artificial paving. He notes a greater presence of the surname in Liguria, with related forms in Piedmont and in Emilia-Romagna and Veneto.

P. Regati agrees with this Latin etymology and places the main concentration in central Liguria, especially in Chiavari. R. Brondolo adds a complementary reading: the surname may have referred not only to those who lived in a loft or solarium, but also to those who built them.

E. De Stefani offers a different perspective centred on Friuli-Venezia Giulia. There the surname is of micro-toponymic origin, derived from the Friulian word solâr or salâr, which designated the granary or loft at the top of the house, and also the flooring in old texts. The first bearers of the surname would have lived in that part of the dwelling. De Stefani further notes an alternative motivation: a possible derivation from the place name Solârs or Salârs, a locality in the comune of Ravascletto. The surname is documented in the Prato Carnico area from the mid-14th century.