Up from the depths…

Leviathan (/lˈv.əθən/; Hebrew: לִוְיָתָן, ModernLivyatan, TiberianLiwyāṯān) is a huge creature referenced in the Tanakh, or the Old Testament.

This word has become synonymous with any large sea monster or creature. In literature (e.g., Herman Melville’s Moby-Dick) it refers to great whales, and in Modern Hebrew, it simply means “whale”. It is described extensively in Job 3:8, Job 40:15–41:26, Amos 9:3, Psalms 74:13–23, Psalm 104:26 and Isaiah 27:1.

Cirlot identifies the creature as a symbol of the primordial world; monstrous and chaotic, and likens it in this regard to the Scandinavian Midgardorm and Mesopotamian Tiamat.

Old Testament references to a huge sea monster, Leviathan (in Hebrew, Liwyāthān), are thought to spring from an ancient myth in which the god Baal slays a multiheaded sea monster. Leviathan appears in the book of Psalms, as a sea serpent that is killed by God and then given as food to the Hebrews in the wilderness, and it is referred to in the book of Job as well. We began equating Leviathan with the political state after the philosopher Thomas Hobbes used the word in (and as the title of) his 1651 political treatise on government. Today, Leviathan often suggests a crushing political bureaucracy. Leviathan can also be immensely useful as a general term meaning “something monstrous or of enormous size.”

More on Wikipedia and good stuff from Merriam-Webster.