The word is parsed as a compound of potos "drunk, drinkable" and rheō "to flow". The zero grade of the latter is rhu- (verbal adjective ῥυτός, action noun ῥύσις), which could be equated with the [ru] of botrus. As in the alternative etymology of the bunch of grapes as "trampled by feet" (see βότρυς / πούς + τρύω), this one etymologizes the natural object through the cultural product drawn from it, wine. It implies two formal manipulations, the change of [b] into [p] (which is also the case in the etymology πούς + τρύω) and a syncope in *ποτο-ρυ-ς (not explicit in our sources). The formulation in Etym. Gudianum (see Parallels) is abridged to a point where one can no longer see that this is the underlying analysis