This name originally designed the primordial abyss, the water-dragon of darkness and chaos, comparable to Tiamat, and Rahab became later a particular demon, inhabitant of the sea, especially associated with the Red Sea, in this case sometimes associated with Leviathan.
It is unclear the difference between Rahab and Tannin in Jewish literature.
This name was also applied to Egypt, and the destruction of the Pharaoh after the exodus of the Israelites from that country, was compared with the slain of Rahab, perhaps a late corruption of Rahab slaying the Pharaoh (the Red Sea drowning his troops).
Rahab is mentioned in the Talmud and the Old Testament, and its etymology is given as "noise", "tumult" and "arrogance".