Fausset's Bible Dictionary
Lamentations 4:3. Τannin , margin "sea calves." Whales and other cetacean monsters are mammalian. Even they give "the breast" to their young; but the Jewish women in the siege, so desperate was their misery, ate theirs (Lamentations 4:10). Τannin is used vaguely for any great monster of the deep. True whales are occasionally seen in the Mediterranean.
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Fausset, Andrew R. Entry for 'Sea Monster'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/s/sea-monster.html. 1949.