From Plutarch's Life of Aristides:

In fine, when he once had opposed Themistocles in some measures that were expedient, and had got the better of him, he could not refrain from saying, when he left the assembly, that unless they sent Themistocles and himself to the barathrum, there could be no safety for Athens.

Harpers Dictionary of Classical Antiquities on Perseus tells us that the barathron was a "deep pit at Athens into which criminals and the dead bodies of executed criminals were cast."

From Forthrights Phrontistery and the Grandiloquent Dictionary, we learn that in English barathrum means an abyss or an insatiable person, i.e., someone who eats as if their stomach were a bottomless pit.