That this psalm was composed at least as late as the 3rd century B.C. is made probable by the name here given to Egypt, Rahab.
In Babylonian mythology "the old serpent goddess ` the lady Nina' was transformed into the embodiment of all that was hostile to the powers of heaven" (Sayce's Hibbert Lectures, p. 283), and was confounded with the dragon Tiamat, "a terrible monster, reappearing in the Old Testament writings as Rahab and Leviathan, the principle of chaos, the enemy of God and man" (Tennant's The Fall and Original Sin, p. 43), and according to Gunkel (Schopfung and Chaos, p. 383) "the original of the ` old serpent ' of Rev. xii.
Well Rahab apparently was the name of an ancient mythical sea monster.