The Biblical leviathan is often considered to be a demon associated with Satan or the Devil, and held by some to be the same monster as Rahab (Isaiah 51:9). The Biblical references to leviathan appear to have evolved from a Canaanite legend involving a confrontation between Baal and a seven headed sea monster which Baal defeats with the aid of Mot, and they also resemble a Babylonian myth in which the storm god Marduk slays the sea monster Tiamat and creates the earth and sky from the two halves of her corpse.
Legend has it that in the banquet after Armageddon, the carcass of the leviathan will be served as a meal, along with the behemoth and the ziz. Leviathan may also be interpreted as the sea itself, with its counterparts behemoth being the land and ziz being the air and aerospace.
Certain Jewish legends consider leviathan as an androgynous dragon that seduced Eve in his male form, and Adam in his female form.
In demonology a leviathan is every aquatic demon. They are great liars. Leviathans can also possess persons, being very difficult to exorcise; they try to possess every person, but especially women.
During sea-faring's Golden Age, European sailors saw Leviathan as gigantic whale-like sea monster that devoured whole ships by swimming around the vessles so quickly as to create a whirlpool.
The word has been reused (not only in literature) over and again:
In Hebrew, leviathan also means a device for washing raw wool.