An Etymological Dictionary of the German Language/Annotated/Tau

by Friedrich Kluge

Tau (1.), neuter (unknown to Swabian and Bavarian), ‘rope, cable,’ Modern High German only; properly a Low German word, based on Old Icelandic taug, ‘cord, rope’ (whence English tow, Dutch touw). The latter is connected with the Teutonic root tuh (tang), in Modern High German ziehen. From the Low German word French touer, ‘to tow a ship,’ is derived. For the words borrowed by High German from Low German see Strand, Boot, &c.

Tau (2.), masculine, ‘dew,’ from the equivalent Middle High German and Old High German tou (genitive touwes), neuter (Middle German also, masculine); corresponding to the equivalent Old Saxon dau, Dutch dauw, Anglo-Saxon deáw, English dew, Old Icelandic dǫgg (Gothic *daggwa is wanting), whence English (dialectic) dag. Teutonic dauwo-, from pre-Teutonic dháwo-, is generally connected with the Sanscrit root dhā̆v, ‘to run, flow, stream.’