κάστωρ

Of unclear origin.

The traditional theory by Kretschmer derives the word from the name Κᾰ́στωρ (Kástōr, “Castor”), who, in Greek mythology, was known as a savior of women, supposedly for the medicinal effect of castor fluid for women's diseases. However, in the annals of Greek mythology, Castor has never been mentioned in relation with beavers, rendering this derivation as tantamount to folk etymology. In addition, as Schrader and Nehring point out, beavers went extinct in Greece long before the Proto-Hellenics had arrived, which would make the concept of a beaver foreign in the Greek context. It is far more likely that the proper noun Castor is derived from the animal name (perhaps at a time when only the name, but not its characteristics like its musk were remembered), rather than the other way around.

However, beavers were mentioned by Herodotus to exist in the North Pontic area, near the Proto-Indo-European homeland, so it is almost certain the Hellenic tribes were familiar with beavers before venturing into Greece. Thus, there is a chance that the word was inherited from a Proto-Indo-European *kestor- (“beaver, musk”), and was preserved only in Greek. A better candidate for a native Pre-Greek word for "beaver" might be λᾰ́τᾰξ (látax). See also Sanskrit कस्तूरी (kastūrī, “musk”), which was borrowed from the derivative καστόριον (kastórion, “castoreum”).^[1]

Note that the main Indo-European word for "beaver", *bʰébʰrus (which did not survive or exist in Hellenic), may be a reduplicative (and thus non-atomic) formation from *bʰerH- (“brown”).

κάστωρ • (kástōr) m (genitive κάστορος); third declension

1. beaver

• → Classical Syriac: ܩܣܛܘܪ (qasṭor)
• → Latin: castor (see there for further descendants)

• “κάστωρ”, in Liddell & Scott (1940) A Greek–English Lexicon, Oxford: Clarendon Press
• “κάστωρ”, in Liddell & Scott (1889) An Intermediate Greek–English Lexicon, New York: Harper & Brothers
• κάστωρ in Bailly, Anatole (1935) Le Grand Bailly: Dictionnaire grec-français, Paris: Hachette
• Woodhouse, S. C. (1910) English–Greek Dictionary: A Vocabulary of the Attic Language‎, London: Routledge & Kegan Paul Limited.
  • beaver idem, page 68.
  • castor idem, page 117.