acheronian

At this moment Dame Caterina appeared, followed by Father Boniface, who brought Salvator a medicine which he had mixed scientifically according to prescription, and which the patient swallowed with more relish and felt to have a more beneficial effect upon him than the Acheronian waters of the Pyramid Doctor Splendiano Accoramboni.

It is probable, for example, that the famous Tartărus, the place so noted in the empire of this god, comes from Tartessus, near Cadiz: the river Lethe not unlikely from the Guada-Lethe, which flows over against that city; and the lake Avernus, or the Acheronian fen, from the word Aharona, importing, at the extremities, a name given to that lake, which is near the ocean.

It simply signifies the ascent of the soul after death into the Olympian halls instead of descending into the Acheronian gulfs.