In Greek mythology, Hades is both the land of the dead and the god who rules there. Hades the god (who the Greeks also called Pluto) is the brother of Zeus and Poseidon, who rule the skies and the seas. The realm called Hades, where he rules with his wife Persephone, is the region under the earth, full of mineral wealth and fertility and home to dead souls. Hades today is sometimes used as a polite term for Hell ("It's hotter than Hades in here!").
1597, in the meaning defined at sense 3
Greek Aidēs, Āidēs, Haidēs