Τάρταρος

Etymology
According to, this word had been fancifully believed to have been invented by Homer with the city of in mind, with a slight change of letters, it being west of the , or , beyond which the sun sinks past  as it enters into Tartarus. A semantic connection of Definition 2 with the doomed, sunken civilization of has not been overlooked.

suggests (at least partly) otherwise: "prob[ably] word of origin, suggestive of something frightful."

Proper noun

 * 1) Tartarus
 * 2) (Christendom) metaphor for Hell