An Etymological Dictionary of the German Language/Annotated/flügge
flügge, adjective, ‘fledged,’ a Low German form for the strictly High German flücke, Middle High German vlücke, Old High German flucchi, ‘able to fly.’ Akin to Middle Dutch vlugghe, with Low German permutation, English fledged; properly a verbal adjective from fliegen, with the meaning ‘capable of flying.’