1580s, fabled river of the Lower World in Greek mythology, from Greek Akheron, the name of several real rivers in addition to being the mythical river of the Underworld. The name perhaps means "forming lakes" (compare Greek akherousai "marsh-like water"), from PIE root *eghero- "lake" (source of Lithuanian ežeras, ažeras, Old Prussian assaran, Old Church Slavonic jezero "lake").
The derivation from Greek akhos "woe" is considered folk etymology. The name later was given to certain rivers in Greece and Italy because they flowed through dismal surroundings or disappeared underground and were thought to be gateways to the Underworld. Related: Acherontic.
