In Medieval bestiaries, the Hippopodes were a tribe of horse-footed men who lived in the mythical islands of the far north with two other legendary races: the Panotti and Oeonae.
Quote
"Crossing the Ripaean Mountains [probably the Carpathians of central Europe] must coast to the left along the shore of the northern ocean until we reach Gadis. In this direction a number of islands are reported to exist [perhaps in the Baltic Sea] . . . [and] the Hippopodes on which people are born with horses’ feet, which gives them their Greek name."
Source
Pliny the Elder, Natural History 4. 94