Carabiner

A carabiner (/kærəˈbiːnər/) or karabiner is a metal loop with a spring-loaded gate used to quickly and reversibly connect components, most notably in safety-critical systems. The word is a shortened form of Karabinerhaken, a German phrase for a "spring hook" used by a carbine rifleman, or carabinier, to attach items to a belt or bandolier.