An Etymological Dictionary of the German Language/Annotated/Flut
Flut, feminine, ‘flood, inundation, billow,’ from the equivalent Middle High German vluot, masculine, feminine, Old High German fluot, masculine; a word common to Teutonic; compare Gothic flôdus, feminine, Old Icelandic flôþ, Anglo-Saxon flôd, masculine, neuter, English flood, Old Saxon flôd, Dutch vloed. Gothic flôdus, from pre-Teutonic plôtú-s, is based upon a Teutonic root flô (from pre-Teutonic plô); compare Anglo-Saxon flôwan, equivalent to English to flow, Old Icelandic flóa, ‘to flow.’ Akin to the Greek 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 Greek πλύνω.