Easton's Bible Dictionary (1897)
Double rebellion, probably a symbolical name given to Babylon (Jer. 50:21), denoting rebellion exceeding that of other nations.
Smith's Bible Dictionary (1863)
(double rebellion), The land of, alluding to the country of the Chaldeans, and to the double captivity which it had inflicted on the nation of Israel.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
MERATHA'IM (double rebellion), a symbolical name for Babylon. Jer 50:21.