E. Rossoni proposes that this surname would derive from a nickname based on the Arabic term ğāmūs ("buffalo"), used perhaps to highlight the physical robustness of the founding ancestor of the lineage, or to identify him as a buffalo breeder. It is a southern surname, typical of Sicily, with a documented presence in San Cataldo and in the Caltanissetta area, in Barrafranca in the Enna area, and in Campobello di Licata in the Agrigento area.

Another source confirms the same Arabic root ğāmūs for the form Giamūs, without adding further information on geographical distribution or meaning.