B. Zuanella explains that this surname is of Slovene origin and derives from the place name Luža, a small locality abandoned some three hundred years ago, situated beside the Clodig-Podlach road, near Costne/Hostne, in the comune of Grimacco. The form Luszach / Luščak originally designated the inhabitant of, or the person coming from, that place, and was formed by adding the Slovene dialect suffix -ščak to the place name Luža. This Slovene noun means "small hollow in the ground with standing water", a marshy or water-rich area, characteristics that can still be observed at that locality. According to Zuanella, the surname is typical of Costne, from where it spread towards the valley of San Leonardo, Cividale del Friuli and the Friulian plain.

E. Rossoni agrees on the Slovene origin and on the derivation from the place name Luža, situated near Costne and Grimacco, in the province of Udine, and notes that the surname is proper to that area.