The ruminations of an idle mind:

Several English words such as potion, potable, potables, poison, derive from the Latin root potare, poto "to drink". In all cases these words are pronounced with a long 'o' as in 'oh'.

The noble hippopotamus, according to OED:

derives from Late Latin hippopotamus, from Greek hippopotamus "riverhorse," an irregular formation from earlier ho hippos potamios "the horse of the river", from hippos "horse" (see equine) + adjective from potamos "river, rushing water"

In turn, the word element potamos- is described:

word-forming element meaning "river," from comb. form of Greek potamos "river," perhaps literally "rushing water," from PIE *pet- "to rush, to fly" (see petition).

Unfortunately, I've been unable to find a resource that indicates how potamos- is pronounced in Greek and Latin. My reasoning is that, like the root potare, the element is pronounced with a long 'o'. However the OED excerpt above suggests the pronunciation might also be "pet-amos".

This raises two questions:

  1. How is potamos- pronounced in Greek, and does it have any relation to the Latin roots potare and poto?

  2. Where does the "paw" in "hippo-paw-tamus" come from? It seems to me that in order to be consistent with other English words, which preserve the poh sound, the pronunciation ought to be "hippo-poh-tamus" or possibly "hippo-pet-amus", and yet this clearly isn't the case.

I realize this subject is more than a little obscure, but any insights would be appreciated.

  • 5
    Some people pronounce the words cot and caught differently; hippopotamus has the vowel of cot, but the spelling aw suggests the vowel of caught.
    – Angelos
    Jul 21, 2016 at 0:38
  • 3
    @COTO No. Cot, coat, and caught all sound distinct for these people (and that includes me).
    – Angelos
    Jul 21, 2016 at 0:45
  • 2
    "poison" doesn't have long "o." As for "hippopotamus," the vowel is short because it's stressed and in the third-to-last syllable. This is a general thing: compare the pronunciation of "o" in "verbose" and "verbosity." It has little to do with the vowel length in Greek or Latin.
    – herisson
    Jul 21, 2016 at 0:46
  • 2
    In essence, people are lazy. It takes more effort to maintain the mouth shape for the second "poe" sound, then switch quickly to the mouth shape needed for "tomus", than it does to let it slide into "pah" and then ease into "tomus".
    – Hot Licks
    Jul 21, 2016 at 1:30
  • 3
    Also, compare the second <o> in hippopotamus to the word pot, which is pronounced as cot
    – user180089
    Jul 21, 2016 at 2:30

1 Answer 1


Latin potare "drink" is from a Proto-Indo-European root *p(e)h3- meaning "drink" (De Vaan), so it is not related to the root *pet- "to rush" that you mentioned for potamos.

The Greek omikron in ποτᾰμός (potamos) is short and would be pronounced short in Latin. The ō in Latin pōtare, however, is long, so the two o's are pronounced differently in Latin.

As to you paw, I don't recognise that pronunciation. The Oxford English Dictionary (2nd edition) has /pɒ/ for the -po- in -potamus, which sounds just like the po- in the word pot. The first -po- is pronounced /pəʊ/ or /pə/.

It should be noted that any Proto-Indo-European root mentioned, such as *pet-, is not to be interpreted as a guide for pronunciation; pronunciation is extremely likely to have changed between Proto-Indo-European (presumably spoken thousands of years ago) and modern English.

  • The pronunciation of the stressed syllable as -paw- sounds a bit like Brooklynese to me. Jul 21, 2016 at 1:21
  • 1
    @Brian: it's more like a traditional Boston accent, where party is pronounced like potty, and potty like paw-tee. Jul 21, 2016 at 2:10
  • Hence, in short, you're saying that the "pot" in "hippopotamus" isn't related to the Latin roots potare and poto, and that what started out as "hippopetamus" due to the *pet- in potamus spuriously changed to "hippopotamus" over the centuries. Is that accurate?
    – COTO
    Jul 21, 2016 at 4:40
  • 2
    @COTO: Yes, except that hypothetical *pet- changed into pot- very, very long ago, probably before writing existed, and before the earliest Greek inscriptions. This isn't about centuries, it's about millennia. The word for "river" in Greek was always potamos, as far as we can tell from Greek writings. And the word hippopotamos was formed (much?) later than potamos. So there was certainly never a spelling hippopetamus. Jul 21, 2016 at 15:40

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