A. Bongioanni notes that the surname derives from a given name of Greek origin, coming from erasmios, meaning "amiable". He also records regional variants: the popular forms of the Veneto are Rásemo and Rásmo, while in the Naples area the forms Ermo and Elmo appear, the latter associated with the figure of Saint Elmo.

V. Blunda agrees on the Greek origin, but starts from the verb eramai, "to love", from which the name Erasmos derives, with the sense of "loved, desired". According to Blunda, the surname arose as the crystallisation of the baptismal name of an ancestor, linked to the Byzantine hagiographic tradition through Saint Erasmus, patron of sailors.