1563, from L.L.
hippopotamus, from Gk.
hippopotamus "riverhorse" (earlier
ho hippos ho potamios "the horse of the river"), from
hippos "horse" +
potamos "river, rushing water" (see
petition). Replaced M.E.
ypotame (c.1300), which is from the same source but via O.Fr.
"Ypotamos comen flyngynge. ... Grete bestes and griselich" ["Kyng Alisaunder," c.1300]