Jamieson, Fausset and Brown on Nahum 3:9

9. Ethiopia--Hebrew, Cush. Ethiopia is thought at this time to have been mistress of Upper Egypt.

Egypt--Lower Egypt.

her strength--her safeguard as an ally.

it was infinite--The resources of these, her allies, were endless.

Put--or Phut (Ge 10:6); descended from Ham (Eze 27:10). From a root meaning a bow; as they were famed as archers [Gesenius]. Probably west of Lower Egypt. Josephus [Antiquities, 1:6.2] identifies it with Mauritania (compare Jr 46:9, Margin; Eze 38:5).

Lubim--the Libyans, whose capital was Cyrene; extending along the Mediterranean west of Egypt (2Ch 12:3; 16:8; Ac 2:10). As, however, the Lubim are always connected with the Egyptians and Ethiopians, they are perhaps distinct from the Libyans. The Lubim were probably at first wandering tribes, who afterwards were settled under Carthage in the region of Cyrene, under the name Libyans.

thy--No's.

helpers--literally, "in thy help," that is, among thy auxiliaries.