The word was recorded in English before 1398, from Latin, and before that, Greek. John Trevisa, translating the medieval encyclopaedia De Proprietatibus Rerum, described a creature that, unlike most fish, left the water at night to feed on land.
An earlier form of the word entered English from Old French around 1300, its spelling altered from the original Greek. The medieval romance Kyng Alisaunder described it as 'wondrous'. By the 1560s the word had been reshaped again, closer to its ancient form.
Behind the Greek word lay two parts. The first traces to a Proto-Indo-European root, *ekwo-, meaning 'horse'. The second traces to a different Proto-Indo-European root, *pet-, meaning 'to rush, or to fly'.
EQUINE and MESOPOTAMIA share the same roots. EQUINE entered English in 1765, from Latin, describing anything relating to horses. MESOPOTAMIA, the ancient region now largely within modern Iraq, takes its name from a phrase meaning 'between two rivers'.
By the 1570s the word also named a heraldic creature, unrelated to the real animal, with the head and forelegs of a horse and the tail of a fish, sometimes shown drawing Neptune’s chariot. This fantastical version appeared on coats of arms for over two centuries, fading from use by 1830. Modern science has since revealed a stranger truth about the real animal, that its closest living relatives are whales.
