Rahab - poetical name for Egypt (see on Isa 30:7).
dragon - Hebrew, tannin. The crocodile, an emblem of Egypt, as represented on coins struck after the conquest of Egypt by Augustus; or rather here, “its king,” Pharaoh (see on Isa 27:1; Psa 74:13, Psa 74:14; Eze 32:2, Margin; Eze 29:3).