Ask Language Log: hippocampus

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Via Jason Schrock on Twitter

hǎimǎ 海马 ("seahorse")

So where does the "Hippocampus" on the pictured language learning card come from? That's the scientific genus name for what is commonly known as the "seahorse". It derives from Greek hippos ("horse") and kampos ("sea monster").

The reason this card leads to a bit of cognitive dissonance for English speakers who see it is that we know the term "hippocampus" better as an important part of the brain that takes its name from the fact that its shape resembles a seahorse. Not too surprisingly, the Chinese word for the brain's "hippocampus" is hǎimǎ tǐ 海马体 (lit., "seahorse body").


hémǎ 河马 (lit., "river horse", i.e., "hippopotamus" < Gk. hippos ["horse"] + potamos ["river"] — completely unrelated to "Potomac", which has an Algonquian derivation).


  1. Victor Mair said,

    April 4, 2015 @ 9:12 am

    Amazing serendipity! You can almost see the hippocampus in the backward brain of the previous post ("Oops").

  2. Jin Defang said,

    April 4, 2015 @ 9:34 am

    Somewhere I read that Potomac is actually an anglicized spelling of the Algonquin name, which was pronounced more like Patowomeck that potamos, and originally referred to the village built there. That John Smith gave the name to the river. But i's still an interesting coincidence.

  3. Plane said,

    April 4, 2015 @ 10:12 am

    In Japanese, 海馬 is somewhat less ambiguous since the usual word for seahorse is タツノオトシゴ, which is also a rather nifty word :-) In kanji, that's 竜の落とし子.

    Of course, there's usually no ambiguity anyway since the two appear in very different contexts.

  4. Taegyung said,

    April 4, 2015 @ 10:54 am

    The Koreans also have two Sino-Korean words "해마"(Haema, 海馬, "seahorse") and "해마체"(Haemache, 海馬體, "hippocampus"), with the traditional version Chinese characters of 海马 and 海马体 . So the Korean and Chinese people can easily know that a hippocampus is named so due to its resemblance to a seahorse.
    I never knew it was Sino-Korean, but the Koreans call a hippopotamus "하마"(Hama), which must be 河馬, with traditional characters of the Chinese hippopotamus, 河马.

  5. Keith said,

    April 4, 2015 @ 1:14 pm

    French uses the word "hippocampe" for seahorse, as well as for that bit of the brain.

    Interestingly, French people also commonly use the word "amygdale" for tonsil as well as for a bit of the brain. Even though there is a word "tonsille", I've never heard anybody use it.

    I wonder what the Chinese, Japanese and Korean terms are for amygdala and tonsils…

  6. Vasha said,

    April 4, 2015 @ 3:28 pm

    German is another language that usually calques Greek technical terms into native morphemes. Didn't do that for hipocampus, surprisingly enough; the seahorse is "Seepferdchen" ("sea horse" + diminutive suffix) but the hippocampus is just "Hippokampus". However, "amygdala" means "almond" in Greek, and the tonsils in German are "Mandeln" ("almonds") and the brain-amygdala is "Mandelkern" ("almond core/kernel/nucleus").

  7. julie lee said,

    April 4, 2015 @ 4:08 pm


    The name of tonsils in Chinese is 扁桃腺, pronounced " bian tao xian" in Mandarin, literally "flattened-shape-peaches gland".

  8. Keith said,

    April 5, 2015 @ 3:52 pm

    Thanks for the information about the Chinese term for "tonsil". I was able to find a WIkipedia article about the amygdala in the brain, using the term 杏仁核.

  9. AG said,

    April 5, 2015 @ 6:04 pm

    I somehow got the impression that "hippocampus" was Greek+Latin for "horse track" when I was a kid, and never questioned it. I always assumed the brain part was shaped like a little hippodrome.

    Whew. Glad this came up before I embarrassed myself in public.

  10. Rodger C said,

    April 6, 2015 @ 7:03 am

    AG, I remember having the same notion. Maybe this was an error found in some commonly read source?

  11. Brett said,

    April 6, 2015 @ 10:50 am

    @Rodger C: There aren't very many English words that begin with "hippo." Kids learn "hippopotamus" early, but if you were learning "hippocampus" and "hippodrome" around the same time, mightn't you just gave gotten the two confused?

  12. Neil Dolinger said,

    April 6, 2015 @ 2:25 pm

    @AG, seems like an entirely plausible guess. Latin used "campus" to refer to fields. It seems to have that sense in PIE, but not sure about Greek. It's not such a long leap from "field" to the notion of a circular track.

  13. Tom said,

    April 8, 2015 @ 6:34 am

    My baby son has a cuddly seahorse named "H.C.", for obvious reasons.

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