Old English otr, otor "otter," from Proto-Germanic *otraz (cognates: Old Norse otr, Swedish utter, Danish odder, Dutch otter, Old High German ottar, German Otter), from PIE *udros, literally "water-creature" (cognates: Sanskrit udrah, Avestan udra "otter;" Greek hydra "water-serpent," enydris "otter;" Latin lutra, Old Church Slavonic vydra, Lithuanian udra, Old Irish odoirne "otter"), from root *wed- (1) "water" (see water, n.1). Sea otter attested from 1660s, also known as sea-ape.