Tartarus

Tartarus was originally a place, situated as far below Hades as heaven was above the earth, to which rebellious Titans were sent.

Later it became synonymous with Hades, and later still it was personified by Hesiod in his Theogony as the offspring of Chaos, together with Gaia (earth) and Eros (love). The name looks easy, but is actually difficult to interpret.

It may be a Cretan word, and somehow linked to one of the place-names containing tar- that lie to the west of Greece, for example Tartessus, an ancient kingdom and sea port near the mouth of the river Guadalquivir in south-west Spain (modern Andalusia).

The name also had its influence on the spelling 'Tartar' (with an V) for a member of the race whose name is more correctly spelt Tatars (itself of Persian origin). (The other 'tartar' meaning 'wine sediment' seems to be related to neither Tartarus nor the Ta(r)tars, but apparently derives from a medieval Greek word tartaron of uncertain origin.)