hippocampus

Etymology

It is borrowed from Latin hippocampus, also hippocampos, a monster with a horse's body and a fish's tail ridden by the sea gods, and also a small fish, the seahorse,^[2][3][4] from Ancient Greek ἱππόκαμπος (hippókampos), a Hellenistic word with the same senses.^[2][5] The Greek word is formed from ἵππος (híppos, “horse”) and κάμπος (kámpos, “sea monster”).^[2][5][6][4] The OED calls kámpos of uncertain origin, perhaps a loanword;^[2] Etymonline and Klein suggest a link with κάμπη (kámpē, “caterpillar”).^[3][5] The Greek for horse goes back to Proto-Indo-European *ekwo- (“horse”).^[3] J. C. Aranzi used the Latin word for a part of the brain in his “De humano foetu” (1587).^[2]

Earliest recorded meaning

A fish with a horse-like head, a seahorse: 1576, in Abraham Fleming's translation of Ravisius in the Panoplie of Epistles.^[2][3]

Semantic evolution

The mythical sea-horse, part horse and part fish or dolphin, often shown drawing Neptune's chariot, is recorded in English from 1606, in a letter of William Drummond;^[2][3][6] Merriam-Webster Unabridged gives it as the first sense.^[6] From 1695 the word named a curved ridge in the floor of a ventricle of the brain,^[2] after its supposed likeness to the fish;^[3] Etymonline dates this sense to 1706.^[3] A second, smaller ridge was called the lesser hippocampus or hippocampus minor from 1798.^[2] In 1758 scientific Latin made Hippocampus the name of the seahorse genus.^[2][7]

Timeline

• 1576 – a seahorse or similar fish.^[2][3]
• 1606 – a mythical creature, part horse and part fish.^[2][6]
• 1695 – a curved ridge in a ventricle of the brain.^[2]
• 1798 – the hippocampus minor, a smaller ridge in the brain.^[2]

Meanings

Noun

1. A curved ridge of grey matter in the floor of each lateral ventricle of the brain, part of the limbic system.^[7][6][2]
2. A legendary sea creature with the head and forelegs of a horse and the tail of a fish or dolphin.^[6][7][2]
3. A seahorse, or any fish of the genus Hippocampus.^[7][2][4]

Word family

• hippocampal

Related words

• hippopotamus
• hippodrome
• seahorse

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins