Meaning

noun the largest or most massive thing of its kind

noun monstrous sea creature symbolizing evil in the Old Testament

originThe noun is derived from Middle English leviathan, levyathan, levyethan, from Late Latin leviathan, a transliteration of Biblical Hebrew לִוְיָתָן (liwyāṯān), possibly from לִוְיָה (liwyâ, “garland, wreath”) + ־תָּן (-tān, suffix forming agent nouns), literally “the tortuous one”. Noun sense 2.2 (“political state”) was coined by English philosopher Thomas Hobbes (1588–1679) in his work Leviathan…

Etymology from Wiktionary, CC BY-SA 3.0