Named after Abdullah Ben Ghashir, due to his majority proprietary holding of the land in the region.
During the Italian colonization of Libya, the Italian army defeated the Libyan resistance in Qasr Bin Ghashir and executed Abdullah Bin Ghashir, taking control and possession of the land and changing the name of the town to "Castel Benito".
In 1947, the name was changed back to Qasr bin Ghashir and all land rights returned to the Libyan Government after Italy relinquished it's claims to Libya as part of the 1947 Peace Treaty.
During the Italian invasion descendants of Abdullah Bin Ghashir travelled to other parts of Libya for safety.
As a safety measure some adapted their surname to alternatives of Bin Ghashir to Ben Gasher, Gashier and Ghasheer.