What is the meaning of "Chorev El Meimeha"?
Radak: This is like "Charvu ha'Mayim" (Bereishis 8:13; it dried up). Since Bavel has much water, it says metaphorically that its water will dry, i.e. its goodness and wealth will cease.
Malbim: The water around the city, for the sake of a siege [will dry up].
Why does it say "Ki Eretz Pesilim Hi"?
Radak: It is because they trusted in their idols.
What are "Eimim"?
Radak: Their idols. They are called Eimim, for their worshippers fear them.
Malbim: They are pictures of bizarre animals that instill fear.
What is the meaning of "Yis'halelu"?
Rashi #1: They will rant and rave [Radak - about the idols and their service].
Rashi #2, Targum Yonasan: They will boast 1 about their giant idols.
Radak: This is astounding. The word implies lunacy and folly, like "va'Yis'holel b'Yadam" (Shmuel I, 21:14) and "v'His'holelu ha'Rechev" (above, 46:9)!