The authors agree that the surname has its origin in the medieval form Nascinguerra, a name attributed to children born during periods of armed conflict, and that in time it became a surname. The form Nassivera represents the evolutionary result of that designation after centuries of use in the Carnia area, the mountainous region of northern Friuli, in the province of Udine.

E. De Stefani notes that the surname has a sporadic presence throughout Friuli, but is especially rooted at Forni di Sotto, in the hamlet of Tredolo. He further documents variants recorded at Udine: Nascinguerra, Nascivera and Nassinvera, which reflect the graphic and phonetic transition from the original form.

E. Rossoni broadens the etymological picture with two additional hypotheses: on the one hand, that the name could have been attributed to a child born after a long wait or after failed pregnancies or births; on the other, that it could be linked to the Latin dies natalis —"day of birth"— with the addition of vera, alluding to an awaited and finally fulfilled birth. Rossoni agrees in noting Forni di Sotto as the most characteristic geographical core of the surname.