B. Zuanella describes this as a surname typical of and endemic to Ponteacco, documented in the parish registers of San Pietro al Natisone. From there it spread to the neighbouring localities of Tiglio, Sorzento and San Pietro al Natisone, and subsequently to Cividale del Friuli and to the rest of the region of Friuli-Venezia Giulia. According to Zuanella, by the middle of the 19th century no fewer than eleven families bearing this surname lived side by side in Ponteacco, all of them probably descended from a certain Simon Juscha recorded in the baptismal registers at the beginning of the 17th century.

The authors agree that the surname is of Slavic origin and is linked to the name Ioachim (Saint Joachim). Zuanella specifies that it arose through the suffix -(j)a applied to the hypocoristic form Juh —also documented as Juch and Jug—, a contracted variant of that name. E. Rossoni agrees that all the variants of the group —among them Iuch, Iug, Juch, Jug and Jussa— are Friulian surnames derived from Slavic contracted and truncated diminutive forms of the name Gioacchino, although he notes that most of those variants have almost entirely died out, while Iussa remains well established in San Pietro al Natisone and Cividale del Friuli.