An Etymological Dictionary of the German Language/Annotated/Fluß
Fluß, masculine, ‘river, stream, flow,’ from Middle High German vluȥ, Old High German fluȥ, masculine, ‘river, stream, cast, bronze cast, rheumatism’; in these senses simply a Modern High German derivative of fließen, pointing to Goth *fluti-. English flyte signifies a peculiar kind of ‘vessel, pontoon.’ For the genuinely Teutonic word for ‘river, flowing water,’ see under Au; compare also Strom.