An Etymological Dictionary of the German Language/Annotated/einzeln
einzeln, adjective and adverb (in Suabian and Bavarian einzächt), ‘single(ly), sole(ly), individual(ly),’ from the equivalent Middle High German einzel, a modification of the older and more frequent einlütze, Old High German einluzzi, ‘single, alone’; compare Thuringian, and Saxon eelitzg (êlizχ), ‘unmarried,’ from Middle High German einlützec (Old High German einluzzo), ‘unmarried.’ The second component belongs to Modern High German Loos (Old High German hlioȥȥan); Old High German ein-luzzi, ‘one whose lot stands alone.’ Compare also Old Icelandic eínhlítr, ‘single’?