Rahab m.n. (Hebrew: רַהַב, Modern Rahav, Tiberian Rahaḇ; "blusterer" is used in the Hebrew Bible to indicate rage, fierceness, insolence, pride.) Rahab is the emblematic name of Egypt and is also used for the sea. In medieval Jewish folklore, Rahab is a mythical sea monster.
Rahab is a poetical name for Egypt. It might have Egyptian origins that were accommodated to the Hebrew language. However, there is nothing revealing in the Coptic language.
I mention Rahab (Egypt) and Babel to those knowing Me, Lo, Philistia, and Tyre, with Cush! This [one] was born there. (Psalm 87:4)YLT
Thou [Jehovah] art ruler over the pride of the sea, In the lifting up of its billows Thou dost restrain them. Thou hast bruised Rahab (Egypt), as one wounded. With the arm of Thy strength Thou hast scattered Thine enemies. (Psalm 89:8–10)YLT
Awake, awake, put on strength, O arm of Jehovah, Awake, as [in] days of old, generations of the ages, Art not Thou it that is hewing down Rahab (Egypt), Piercing a dragon! (Isaiah 51:9)YLT
Prior to the Medieval adoption of "Rahab" to mean demon or sea beast, the name also appears in Psalms: 104, Psalms 89: 5-12, and Isaiah 51:9-10. Rahab, in these passages, takes the meaning of primeval, chaotic, multi-headed sea dragon or Leviathan. It can be assumed that long before the Jewish mythos, the ancient Jews emulated the creation fables told by their predecessors. The Babylonians, for example, told of a thunder god, Marduk, and a sea beast, Tiamat, battling for supreme power over the other gods, in the Enûma Eliš. It can be speculated these two characters in the Babylonian myth are parallel to the creation stories found in the Biblical passages containing the name Rahab.