The LORD of hosts hath sworn by himself, saying, Surely I will fill thee with men, as with caterpillers; and they shall lift up a shout against thee.
The Lord of hosts hath sworn by himself - literally, by His soul (2 Samuel 15:21; Hebrews 6:13, "Because He (God) could swear by no greater, He sware by Himself").
I will fill thee with men, as with caterpillars - locusts (Nahum 3:15). Numerous as are the citizens of Babylon, the invaders shall be more numerous.