The name Rahab comes from the Hebrew רחב (rāḥāḇ), where it is the name for the sex worker from Jericho that agrees to hide the Israelite spies sent by Joshua in exchange for her life in Joshua 2. The meaning of Rahab's name is disputed, and may be a reference to the action she took in assisting the Israelites in "opening" the walls of Jericho in order to destroy it.

The name most likely comes from the Hebrew verb רחב (rāḥaḇ), which means "to open oneself, grow wide or large." It is used in reference to opening the mouth in praise (cf. 1 Samuel 2:1; Isaiah 60:5), and is often used in relation to open or wide areas of land (cf. Isaiah 30:23; Ezekiel 41:7). The city of Rehov (now Tel Rehov) in the broad Bet Sheʾan Valley and mentioned in Numbers 13:21 is one of the largest ancient tells excavated to date in Israel. The noun רחב (rāḥāḇ) means "broad space, expanse," as in Job 36:16 and 38:18, while the word רחב (roḥāḇ) is the Hebrew word for "breadth."

This name should not to be confused with the Rahab (רהב, rāhaḇ, with a medial heh, not a ḥet) that shows up in poetic verses as a representation of Egypt (Psalm 87:4; Isaiah 30:7) or the primordial chaotic beast that the Lord defeated at creation (Psalm 89:10; Isaiah 51:9; Job 9:13, 26:12). This name probably derives from the mythical monster רהב (rāhaḇ), whose name means "one who surges" or "one who acts stormily, boisterously, arrogantly," and is typically represented in opposition to the Hebrew deity.