[1]1925 Jewish Encyclopedia, Gehenna
The place where children were sacrificed to the god Moloch … in the "valley of the sons of Hinnom," to the south of Jerusalem (Josh. xv. 8, passim; II Kings xxiii. 10; Jer. ii. 23; vii. 31-32; xix. 6, 13-14). … the valley was deemed to be accursed, and "Gehenna" therefore soon became a figurative equivalent for "hell." Hell, like paradise, was created by God (Sotah 22a);[“Soon” in this paragraph would be about 700 BC +/-, DA]
From the same Jewish Encycllopedia article.
“… heretics and the Roman oppressors go to Gehenna, and the same fate awaits the Persians, the oppressors of the Babylonian Jews (Ber. 8b).[Talmud] “When Nebuchadnezzar descended into hell, [שאול/Sheol] all its inhabitants were afraid that he was coming to rule over them (Shab. 149a; [Talmud] comp. Isa. xiv. 9-10).