An Etymological Dictionary of the German Language/flößen
flößen, flötzen, vb., ‘to float (timber), skim (milk),’ from MidHG. vlœȥen, vlœtzen, ‘to cause to flow, wash down (soil),’ factitive of fließen. The MidHG. forms with ȥ and tz correspond to those of heißen, reißen (MidHG. heiȥen-heitzen, reiȥen-reitzen), and are based upon a Goth. inflexion flautja, flauteis, since tj leads, through the medium of tt, to HG. tz, but t without j to ȥ.