As with many other scriptures, maybe we have all been incorrectly taught the traditions of men regarding "hell". Sheol, translated as "hell" in the KJV is equated with "death" in the couplet of 2 Sam. 22:6,

"The sorrows of hell compassed me about; the snares of death prevented me;" (KJV)

"Sheol" is Strong's Hebrew 7585 and according to Brown-Driver-Briggs means the underworld, or the condition of the wicked who are consumed or waste away, and also as a place of the deep or a pit. Source: here

Making connections from the scriptures:

Josh. 18:16, in describing the land still to be allotted to seven of the tribes of Israel,

"And the border came down to the end of the mountain that lieth before the valley of the son of Hinnom, and which is in the valley of the giants on the north, and descended to the valley of Hinnom, to the side of Jebusi on the south, and descended to Enrogel," (KJV)

The valley of the giants, whom Caleb slew and was then granted their land for his portion, was also called the valley of the Rephaim.

Josh. 14:12-15, Caleb reminding Joshua of God's promise -

"12 Now therefore give me this mountain, whereof the LORD spake in that day; for thou heardest in that day how the Anakims were there, and that the cities were great and fenced: if so be the LORD will be with me, then I shall be able to drive them out, as the LORD said.

13 And Joshua blessed him, and gave unto Caleb the son of Jephunneh Hebron for an inheritance.

14 Hebron therefore became the inheritance of Caleb the son of Jephunneh the Kenezite unto this day, because that he wholly followed the LORD God of Israel.

15 And the name of Hebron before was Kirjatharba; which Arba was a great man among the Anakims. And the land had rest from war."

Josh. 15:8,

" and the border hath gone up the valley of the son of Hinnom, unto the side of the Jebusite on the south (it [is] Jerusalem), and the border hath gone up unto the top of the hill-country which [is] on the front of the valley of Hinnom westward, which [is] in the extremity of the valley of the Rephaim northward;" (YLT)

Josh 15:13-14,

"13 And unto Caleb the son of Jephunneh he gave a part among the children of Judah, according to the commandment of the LORD to Joshua, even the city of Arba the father of Anak, which city is Hebron.

14 And Caleb drove thence the three sons of Anak, Sheshai, and Ahiman, and Talmai, the children of Anak." (KJV)

The sons of Anak, the Anakim, were giants. The land of Hebron -the same as Kirjatharba - was previously held by the Anakim.

Deu. 2:10-11,

"10 `The Emim formerly have dwelt in it, a people great, and numerous, and tall, as the Anakim;

11 Rephaim they are reckoned, they also, as the Anakim; and the Moabites call them Emim." (YLT)

The Rephaim were as tall as the Anakim, and were also called the Emim by the Moabites, and Zamzummim by the Ammonites (Deu. 2:20)

The valley of the giants, the valley of the Rephaim was a land of slaughter and pagan sacrifice. The valley of the Rephaim was also where many battles with the Philistines were fought. (S Sam. 5:18, 22; 23:13; 1 Chron. 11:15, 14:9).

It was a place of destruction and death.

References to the Rephaim became known as speaking of the dead. The giants had been slaughtered, and the use of that name became known for those who had died and been wiped out, desolated, destroyed. The Rephaim was symbolic of the state of dead and destroyed souls.

As the valley of Hinnom (the valley of the giants) had begun as a place of fire and burning and slaughter of the wicked, then reference of gehenna is to the slaughter, the act of desolation and ultimate destruction.

From "The Fires of Gehenna: View of Scholars" by Todd Bolen,

"The first is Edward Robinson, preeminent explorer of the Holy Land beginning in 1838. He wrote: “In these gardens, lying partly within the mouth of Hinnom and partly in the Valley of Jehoshaphat, and irrigated by the waters of Siloam, Jerome assigns the place of Tophet; where the Jews practised the horrid rites of Baal and Moloch, and ‘burned their sons and their daughters in the fire.’ It was probably in allusion to this detested and abominable fire, that the later Jews applied the name of this valley (Gehenna), to denote the place of future punishment or the fires of hell. At least there is no evidence of any other fires having been kept up in the valley; as has sometimes been supposed” (Biblical Researches, vol. 1 [1841], 404-5).

The origin of the “garbage dump” theory appears to be Kimchi. James A. Montgomery observes this medieval commentator’s logic, but does not accept it.

“With the common sense which often characterizes Jewish commentators, Kimchi says that the place was the dump of the city, where fires were always kept burning to destroy the refuse; ‘therefore the judgment of the wicked is parabolically called Gehenna.’ But from the Biblical references the place appears to have nothing physically objectionable about it; in contrast to its contemporary condition Jeremiah prophesied that it would one day be called ‘Valley of Slaughter’” (“The Holy City and Gehenna,” JBL 27/1 [1908], 34)." Source: here

The focus, then, was of destruction; not continual torment - but permanent destruction. This is as the Holy Spirit used it in Isa. 17:5 concerning the destruction of Damascus:

" And it shall be as when the harvestman gathereth the corn, and reapeth the ears with his arm; and it shall be as he that gathereth ears in the valley of Rephaim." (YLT)

The valley of the Rephaim, or the valley of the giants, or the valley of Hinnom, or the valley of slaughter, or Gehenna. They were all the same place; the place of destruction.

Rev. 21:8,

" But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death." (KJV)

Matt. 10:28,

" `And be not afraid of those killing the body, and are not able to kill the soul, but fear rather Him who is able both soul and body to destroy in gehenna." (YLT)

The second death equals Gehenna.

Jude 1:7,

" Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire." (KJV)

Fire was always a symbol of God's judgment (Deu. 4:24; 32:22; Ezek. 38:19; Jer. 21:12; Heb. 12:29).

Lam. 2:4,

" He hath bent his bow like an enemy: he stood with his right hand as an adversary, and slew all that were pleasant to the eye in the tabernacle of the daughter of Zion: he poured out his fury like fire." (KJV)

All of the references to fire in the NT is the symbol of God's judgment. God's judgment is the first association we should make with the word "fire". The never ceasing fire, the eternal fire is symbolic of God's never-ceasing and eternal judgment. Once He pronounces judgment it is an eternal judgment, and cannot be undone.

So, as His fire / judgment is permanent, then those condemned to the second death have been permanently destroyed by the fire of God's judgment.

The traditional teaching of most churches that "hell" is a place of eternal torment is not hermeneutically sound. As the first death is a separation of the soul from the body, the second death is everlasting separation of the soul from God. It does not mean it is a state of permanent torment, although He will do whatever He decides with the condemned soul.

Once that sentence of judgment has been pronounced the separation is permanent / eternally and forever determined. The sentence of judgment is the eternal state / condition. What happens to that soul afterward ...we don't know. That is up to God. He mentions "outer darkness" in Matt. 22:13, and "mist of darkness" in 2 Pet. 2:17.

Everlasting death, everlasting separation is a state of darkness where there is no light. As nothing can live without light, the second death may very well indicate the permanent destruction of the condemned soul.

Rev. 21:23-24,

" And the city had no need of the sun, neither of the moon, to shine in it: for the glory of God did lighten it, and the Lamb is the light thereof. 24 And the nations of them which are saved shall walk in the light of it: and the kings of the earth do bring their glory and honour into it." (KJV)

There is more scripture regarding the giants in a post at my blog - "Giants: Rephaim, Zamzummin, Emim, Anakim, Nephilim, Zuzim" here.

You may also be interested in the judgment language of God discussed in Parts III & VI of "It's Not The End of The World" here and here.

(All bold emphasis is mine.)