An Etymological Dictionary of the German Language/Flut
Flut, f., ‘flood, inundation, billow,’ from the equiv. MidHG. vluot, m., f., OHG. fluot, m.; a word common to Teut.; comp. Goth. flôdus, f., OIc. flôþ, AS. flôd, m., n., E. flood, OSax. flôd, Du. vloed. Goth. flôdus, from pre-Teut. plôtú-s, is based upon a Teut. root flô (from pre-Teut. plô); comp. AS. flôwan, equiv. to E. to flow, OIc. flóa, ‘to flow.’ Akin to the Gr. root πλω in πλώ-ω, ‘to float, sail, πλωτός, ‘floating, sailing, navigable.’ Perhaps this Aryan root plô is related to the Aryan root plu mentioned under fließen and Fluder; yet there is no direct connection between Flut and fließen and Gr. πλύνω.