Originally Posted by BritinAfrica

In the past the nickname "Rock Ape" has been attributed to their traditional role guarding areas of Gibraltar, but this is not so. The term came into use after an accident in the Western Aden Protectorate in November 1952.

Two Regiment officers serving with the APL at Dhala decided to amuse themselves by going out to shoot some of the hamadryas baboons (locally referred to as "rock apes"). The officers drew rifles and split up to hunt the apes, yet in the semi-darkness one of the officers fired at a moving object in the distance. When he reached the target he discovered he had shot the other officer. After emergency treatment Flight Lieutenant Percy Henry Mason survived to return to service a few months later. When asked why he had fired at his friend by a board of inquiry the officer replied that his target had "looked just like a rock ape" in the half light. The remark soon reverberated around the RAF and it was not long before the term was in general use.