Allen key
From Longman Dictionary of Contemporary EnglishAllen keyAl‧len key /ˈælən kiː/ noun [countable] British English a tool used to turn an Allen screw SYN Allen wrench American EnglishExamples from the CorpusAllen key• A sheet metal punch is drawn through by being tightened with an Allen key.Origin Allen key (1900-2000) From the Allen Manufacturing Company of Hartford, Connecticut, USA