An Etymological Dictionary of the German Language/Annotated/schleunig
schleunig, adjective, ‘hasty, speedy,’ from Middle High German sliunec, Old High German slûnîg, ‘quick, speedy,’ in Old High German also ‘thriving.’ A lengthened form of Gothic *slû-na-, for which we have, however, snû-na-; the l seems to have been produced by assimilation on account of the suffix n. Allied to the Old Teutonic root snū̆, ‘to hasten, move quickly, turn’; compare Old High German sniumo, Anglo-Saxon sneóme, adverb, ‘speedily, quickly,’ Gothic sniumundô, ‘hastily,’ as. snûde, adverb, ‘quickly’; as a verb sniumjan, ‘to hasten,’ Gothic sniwan, ‘to hasten,’ Anglo-Saxon sneówian, ‘to hasten,’ Old Icelandic snúa, ‘to turn.’