According to E. Rossoni, it derives from the place name Barlassina (Milan area). The lineage of the Da Barlassina is documented in Monza from the 15th century. The place name is still of unknown origin, while the oldest form is Barnaxina, which some scholars compare with Barni, another still obscure place name. The Da Barnaxina are already established in the Monza area in the 14th century and, in particular, there are several merchants, some engaged in wool weaving, a maestro di muro (foreman) and a caleghar, that is, a shoemaker.