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hippo-

a combining form appearing in loanwords from Greek, where it meant “horse” (hippodrome); on this model, used in the formation of compound words (hippology).

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Also especially before a vowel, hipp-.

Origin of hippo-

< Greek: combining form of híppos; cognate with Latin equus, Old Irish ech, Old English eoh, Sanskrit aśvas, Lithuanian ašvà
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Word Origin and History for hippo-

before vowels, hipp-, word-forming element meaning "horse," from Greek hippo-, from hippos "horse," from PIE *ekwo- (see equine).

Online Etymology Dictionary, © 2010 Douglas Harper