This is not a reference to the Rahab in the book of Joshua. Elsewhere in Scripture, Rahab
was the name for a sea monster who embodied and symbolized dynamic powers asserted against God (Psalm 89:11; Job 9:13; Job 26:12; Isaiah 51:9).1 In Isaiah 30:7, Rahab is identified with Egypt and this is likely what is meant here.
4 Among those who know me I mention Rahab and Babylon; behold, Philistia and Tyre, with Cush “This one was born there,” they say.