means A small, curved structure deep in the brain that plays a central role in forming new memories and in spatial navigation; it's also the anatomical name for the seahorse genus.

from From Greek 'hippokampos,' stitched together from 'hippos' (horse) and 'kampos' (sea monster) — the mythical sea-horse that drew Poseidon's chariot. Sixteenth-century anatomists, peering at this ridge of brain tissue and finding it eerily seahorse-shaped, borrowed the creature's name. The seahorse itself had already inherited the word, so the brain and the fish are cousins, both named for a monster that never existed.