An Etymological Dictionary of the German Language/flott

by Friedrich Kluge

flott, adj., ‘afloat; merry, luxurious,’ first occurs in ModHG. from LG.; comp. Du. vlot, ‘floating, swimming’; it is connected with fließen, Floß, but has, like Flotte, Sax. the dental medially, hence it must be assumed that the word was borrowed from LG.