> and hippo, from the latin root, I knew was not as obvious as the animal, but probably something like "large" (clue: the Hippodrome)

Well.. Hippos is greek for horse, and Hippopotamus is a "river horse". Same for Hippodrome, a course for horses. And in latin, hypo means small (and not large), as seen in e.g. hypoglycemia.

And I thought in German Nilpferd (horse from the Nile) sounded ridiculous. It is almost the same as the original. TIL

Hypo is Greek too, not Latin "small" for a latin radical would be "mini" (from "minus") like in miniature, minuscule, etc.