The bible doesn’t say the afterlife is permanent, when people die they are awaiting the resurrection. The righteous go to paradise awaiting the 1st resurrection/rapture when they get new heavenly bodies (1 Cor 15:12-58, 1 Thess 4:13-18, Heb 11:32-35, Rev 20:4-6). Meanwhile the unsaved await the 2nd resurrection in Hell/Hades/Sheol, which then leads to the second death in the Lake of Fire (Rev 20:4-6, Rev 20:11-15). Hell/Hades/Sheol is a temporary holding place of the unsaved until the 2nd resurrection [of the wicked] (Rev 20:4-6, Rev 20:11-15). Then the wicked are condemned to the Lake of Fire, along with Satan; joining the Anti-Christ and False Prophet who were thrown in beforehand. Revelation 19:20, 20:10-15, and 21:8 explain the Lake of Fire and say the hell itself is also thrown into the Lake of Fire on judgment day, which means there are two separate locations and only one of them is a permanent stay.
Hell in the KJV Bible is actually translated from 4 different words:
Sheol (שְׁאוֹל), Gehenna (γέεννα), Hades (ᾍδης), and Tartarus (ταρταρώσας)
Sheol (Hebrew) and Hades (Greek) are mutually interchangeable are referring to the state of the dead who are awaiting their resurrection and judgment. The Book of Revelation describes Hades being cast into the Lake of Fire (Revelation 20:14). Gehenna is often used when Jesus (and James in James 3:6) are referencing the Lake of Fire. This is the eternal place of damnation for those who reject God’s salvation. Those people are sent here after judgment day along with all rebels against God. Tartarus is only used once and it is a cultural reference to Greek mythology. Peter used this word to connect the spiritual rebels (fallen angels or Nephilim) from Genesis 6:4-5 who rebelled against God and conceived giants with humans to the Titans who gave birth to the ”gods” in Greek myth. Peter is likely referencing these things because there is a Gentile audience who come from a Greek cultural background and they aren’t as familiar with the Torah and Jewish theology. Paul does this as well a few times he references the Greek poet and prophet Epimenides in Titus 1:12 and Acts 17:28.
Generically speaking Hell comes from various old European language cognates for the afterlife. It is just that, a word for after-life that the Anglo-speaking people could recognize. This is true for translations of any written work in general. When translating between languages, not every word has an equivalent on both sides. Common words for the human experience usually exist in all languages like death, life, birth, sex, food, sleep, person, animal, plants, sun, moon, water, sky, earth, etc. However, there are words that only exist in one language because the language/culture invented that concept. For example, words like Qi/Chi(氣) and chakra (चक्र) do not have Western equivalents so Westerners simply use the same words. Likewise, with modern technology, most languages outside of English use a variant of the word Television or Te-Ve, when referring to a Television because TVs were invented by English speakers in the West. The same is true for inventions like telephones and computers. Since English is a Germanic language, the word “hell” in English comes from one of the Old Germanic words for afterlife including but not limited to hel (Old Norse), hellia (Old Saxon), and halja (Gothic). The old Norse Hel, is probably most familiar to people. It refers to Helheim, an extremely cold place where the souls of the dead go if they don’t go to Valhalla, in Norse mythology. Hel is also the name of the goddess of death who rules Helheim. Greek has a similar system where Hades is both a place and the god of the underworld. Death in the Old Norse language is dauði, which is likely derived from the proto-Germanic *dauþuz, which is where we get our word “death” in English.
The word grave or death is translated from the Hebrew word Sheol (שְׁאוֹל). Note: Sheol is the word for the state of being already dead, not “death” as in the verb to die, that word is Maveth (מָוֶת). When the Septuagint translators were making the Greek bible, they use the closest word Greek had to offer, which was Hades (ᾍδης). The word for death/dying in Greek is Thanatos (θάνατος) which is also the name of the Greek god of death, meanwhile, Hades is the habitat of the dead (the underworld) and the named after the god that rules the underworld. Hades and Sheol are referring to what happens to people who are dead, not the verb death itself, so Hades fits the definition of what Sheol would mean to a Greek speaker. In Greek translations of the bible, Hades is not referring to the Greek mythology definition of the underworld or the god that rules it, but rather it is simply a word that means a state of death, or place for the dead. Likewise, Hell is not referring to the ice-cold Helheim of the Nordic people, but simply the linguistic equivalent of Sheol in Germanic languages like English.
Gehenna (Valley of Hinnom in the Old Testament) is the name of a place in Jerusalem. In the Old Testament, some of the kings of Judah sacrificed their children (Jeremiah 7:31, 19:2–6), and every since the place was considered cursed by the time of the 1st Century. Jews of the 1st century would go there to burn garbage. This is typically understood as a reference to the Lake of Fire from the book of Revelation by most bible scholars today. When Jesus used the word Gehenna he was using a physical place on earth as a reference to the Lake of Fire in Revelation 20, which is where the wicked go after judgment. Although some Christian scholars have suggested that Gehenna is actually a prophetic metaphor for the horrible fate that awaited the many civilians killed in the destruction of Jerusalem in 70 CE. This is one of many debates about the eternal judgment of the Lake of Fire.
Tartarus is used once by Peter in 2 Peter 2:4 when explaining how God punished the spiritual rebels (fallen angels) by imprisoning them. It’s likely he used this word to invoke a distinction between Hades/Sheol where humans go when we die, and the prison for spiritual rebels (Fallen Angels, Nephilim, Demons, etc), where they await final judgment. In Greek myth, the word Tartarus refers to (from Wiki): “the deep abyss that is used as a dungeon of torment and suffering for the wicked and as the prison for the Titans. Tartarus is the place where, according to Plato’s Gorgias (c. 400 BC), souls are judged after death and where the wicked received divine punishment.” Peter could have been using this word to equivalate the Titans with the Nephilim. When Christian missionaries traveled the world and encountered various languages, cultures, and religions, they needed to learn their words and belief systems in order to find equivalent concepts and words, so that they could share the gospel with them effectively. So Peter is likely using this Greek myth word to explain the fact that while Judeo-Christianity is monotheistic, there are other spiritual beings, but none of them are considered gods. These beings are creations and servants of God like us, but when they rebel they don’t get a second chance and are waiting for judgment in a harsher prison separate from the place of the rebellious humans who rejected God’s mercy and salvation awaiting their own judgment. This could be a reference to Abaddon (Apollyon in Greek), which is defined as an Angel governing the “bottomless pit” in Revelation 9:11.
In Luke 16:19-31 Jesus describes Sheol or what we call “Hell” (or Hades). This a is temporary holding place (some people interpret it as soul sleep) until the two final resurrections. The righteous people that died went to Abraham’s bosom or paradise, which was separated from the place for the wicked by a chasm, collectively the whole place is Sheol (Luke 16:22-23). The righteous are awaiting the resurrection with the new bodies (Rom 8:23, 1 Cor 15:35-58, 2 Cor 5:1-10, Phil 3:20-21), then they will be raptured into heaven (1 Thess 4:13-18), and will return with Jesus to rule over the earth in New Jerusalem for 1000 years (Rev 20:5-6). The wicked that died are resurrected after the 1000-year reign of Christ (Rev 20:6) and judged and cast into the lake of fire when the world is destroyed and the new heaven and earth are made (Rev 20:7-15, Rev 21:1-8).
Separate observation:
In Greek mythology, there is a paradise for righteousness within Hades called Elysium like Abraham’s bosom. There seems to be a parallel between Abraham’s bosom in Sheol in the bible, and the Elysium in Hades in Greek myth.
On Abraham’s bosom:
https://jamwheeler.com/bible-study/rich-man-and-lazarus-hades-and-abrahams-bosom/
On Gehenna, Hades, and Tartarus
https://www.followintruth.com/the-soul-immortal-soul-hell-and-eternal-conscious-punishment-part-2-of-2
Christian Scholars on Gehenna:
Gregg, Steve (2013). All You Want to Know About Hell. Nashville, TN: Thomas Nelson. pp. 86–98. ISBN 978-1401678302.
Wright, N. T. (1996). Jesus and the Victory of God: Christian Origins and the Question of God, Volume 2. Minneapolis: Fortress Press. pp. 454–55, fn. #47. ISBN 978-0281047178.
Ellicott’s Commentary for English Readers (Matthew 5:22)
“Of hell fire.–Literally, of the Gehenna of fire. Great confusion has arisen here and elsewhere from the use of the same English word for two Greek words of very different meanings: (1) Hades, answering to the Sheol (also for the most part translated “hell”) of the Old Testament, the unseen world, the region or state of the dead, without any reference to their blessedness or misery; (2) Gehenna, which had come to represent among the later Jews (not in the time of any Old Testament writer) the place of future punishment. The history of the word is worth studying. Originally, it was the Greek form of Ge-hinnom (the Valley of Hinnom, sometimes of the “son” or the “children” of Hinnom), and was applied to a narrow gorge on the south of Jerusalem (Joshua 15:8). There Solomon erected a high place for Molech (1Kings 11:7). There the fires of that god had received their bloody offerings of infant sacrifice under Ahaz and Manasseh (2 Kings 16:3; 2 Chronicles 28:3; 2 Chronicles 33:6). Josiah, in his great work of reformation, defiled it, probably by casting the bones of the dead and other filth upon it (2 Kings 23:10-14); and the Jews on their return from captivity showed their abhorrence of the idolatry of their fathers by making it, as it were, the place where they cast out all the refuse of the city. Outwardly, it must have been foul to sight and smell, and thus it became, before our Lord’s time, a parable of the final state of those in whom all has become vile and refuse. The thought first appears in the Targum or Paraphrase of Isaiah 33:14 (“Gehenna is the eternal fire”). It is often said that fires which were kept burning to consume the solid refuse added to the horror of the scene; but of this, though it is suggested by this passage and Mark 9:48. there is no adequate evidence. Here the analogy of the previous clauses suggests also the thought that the bodies of great criminals were sometimes deprived of burial rites, and cast out into the Valley of Hinnom; but of this, too, there is no evidence, though it is in itself probable enough. In any case, the meaning of the clause is obvious. Our passing words, expressing states of feeling, and not the overt act of murder only, are subject to the judgment of the Eternal Judge, and may bring us into guilt and a penalty like that of the vilest criminals.”