Adam Clarke on Jeremiah 50:21

Go up against the land of Merathaim - and against the inhabitants of Pekod - No such places as these are to be found any where else; and it is not likely that places are at all meant. The ancient Versions agree in rendering the first as an appellative, and the last as a verb, except the Chaldee, which has Pekod as a proper name. Dr. Blayney translates: - "Against the land of bitternesses, go up:

Upon it, and upon its inhabitants, visit, O sword!"

Dr. Dahler renders thus: - "March against the country doubly rebellious,

And against its inhabitants worthy of punishment."

The latter of these two versions I take to be the most literal. The words are addressed to the Medes and Persians; and the country is Chaldea, doubly rebellious by its idolatry and its insufferable pride. In these two, it was exceeded by no other land.