The authors agree that the surname derives from the Germanic given name Gisulfo, compounded from two elements: the first, gis, meaning "spear" or "arrow/dart", and the second, wulf or ulf, meaning "wolf" or "warrior".

A. Bongioanni specifies that the first element is gis ("spear") and not gisal ("hostage"), and documents the name in medieval sources such as Paul the Deacon —in the form Gisulfus— and in documents from Benevento and Volterra of the 8th century —as Gisolfus and -solphus. He further notes that the name gained popularity in Cividale, in the region of Friuli-Venezia Giulia, after the discovery in 1874 of a Lombard tomb which local people attributed to Gisulf II, duke of Friuli. Among the variants of the surname he mentions Ghisolfi, documented in the Mondovì area, as well as Solfi, Sulfo, Zizolfo, Suffo and Chisolfi.

V. Blunda characterizes the surname as Sicilian and presents it as a phonetic variant of Ghisolfi, with a vocalization proper to southern Italian. As historical context he adduces the figures of two Lombard princes who kept an autonomous political organization alive in the south of the Italian peninsula even after the fall of the northern Lombard kingdom to Charlemagne in 774: Gisulf I of Benevento, of the 8th century, and Gisulf II of Salerno, of the 11th century.