E. De Stefani notes that the surname derives from a nickname taken from the Venetan sgnaolàr ("to meow") and sgnaolìn ("newborn, very small and slight person"). He also links it with the Friulian gnaulâ, sgnaolâ ("to meow"), which was also used in the sense of "to whimper." From this perspective, Sgnaolìn would have been a nickname applied to one who complained frequently, and over time it became a surname. De Stefani documents its presence in the Triveneto, including the Carnia —a mountainous zone of northern Friuli, in the province of Udine—, with a record in Tolmezzo, among other localities.

E. Rossoni circumscribes the surname to the Venice area, with a presence in Musile di Piave, San Donà di Piave, Fossalta di Piave and Martellago. He considers that it derives from an archaic Venetan dialect nickname based on the term sgnaolin, with the sense of "whine" or "one who acts in a whining way to obtain something." Rossoni also records the form Sgnaolini, of almost unique use, as an Italianization of the original surname.