I was thinking of that the other day as a good example of bias. It embodies an etymological fallacy that ignores usage, the Matthean context (cf. earlier references to weeping and gnashing of teeth in eschatological punishment with fire in Matthew), and the closest parallels in Jewish and Christian literature. Here are some examples with kolasin (or the root verb) and aioniòn, and note also the explicit connection to suffering and torture:
"Many will come from the east and the west, and will take their places at the feast with Abraham, Isaac and Jacob in the kingdom of heaven. But the subjects of the kingdom will be thrown outside, into the outer darkness (eis to skotos to exóteron), where there will be weeping and gnashing of teeth (ho klauthmos kai ho brugmos tón odontón).... The Son of Man will send out his angels, and they will weed out of his kingdom everything that causes sin and all who do evil. They will throw them into the fiery furnace (kaminon tou puros), where there will be weeping and gnashing of teeth (ho klauthmos kai ho brugmos tón odontón). Then the righteous will shine like the sun in the kingdom of their Father... It is better for you to enter life maimed or crippled than to have two hands or two feet and be thrown into eternal fire (to pur to aiónion)... It is better for you to enter life with one eye than to have two eyes and be thrown into the fire of Gehenna (eis tén geennan tou puros).... When the Son of Man comes in his glory, and all the angels with him, he will sit on his throne in heavenly glory. All the nations will be gathered before him, and he will separate the people one from another as a shepherd separates the sheep from the goats ... Then he will say to those on his left, 'Depart from me, you who are cursed, into the eternal fire (eis to pur to aiónion) prepared for the devil and his angels' ... Then they will go away to eternal punishment (eis kolasin aiónion), but the righteous to eternal life" (Matthew 8:11-12,13:41-43, 18:8-9, 25:31-32, 41, 46; written in the late first century AD).
"He shall raise all men from the dead, and appoint some to be incorruptible, immortal, and free from sorrow in the everlasting and imperishable kingdom; but shall send others away to the everlasting punishment of fire (eis kolasin aiónion puros)" (Justin Martyr, Dialogue with Trypho, 117.3; written in c. AD 155).
"Each man goes to everlasting punishment (aiónian kolasin) or salvation according to the value of his actions. If all men knew this, no one would choose wickedness even for a little, knowing that he goes to the everlasting punishment of fire (aiónian dia puros katadikén); but would by all means restrain himself, and adorn himself with virtue" (Justin Martyr, 1 Apology 12.1-2).
"Even when the martyrs were so torn by whips that the internal structure of their flesh was visible as far as the inner veins and arteries, they endured so patiently that even the bystanders had pity and wept. But they themselves reached such a level of bravery that not one of them uttered a cry or a groan, thus showing to us all that at the very hour when they were being tortured (basanizomenoi) the martyrs of Christ were absent from the flesh, or that the Lord was conversing with them. And turning their thoughts to the grace of Christ they despised the tortures (basanón) of this world, purchasing at the cost of one hour an exemption from eternal punishment (tén aiónion kolasin)....But Polycarp said: 'You threaten with a fire that burns only briefly and after just a little while is extinguished, for you are ignorant of the fire of the coming judgment and eternal punishment (to tés mellouses kriseós kai aióniou kolaseós pur), which is reserved for the ungodly' " (Martyrdom of Polycarp 2:2-3, 11:2; written c. AD 155-160).
"Then you will see that though your lot of on earth, God lives in heaven, then you will begin to declare the mysteries of God ... and condemn the deceit and error of the world, when you realize what the true life in heaven is, when you despise the apparent death here on earth, when you fear the real death, which is reserved for those who will be condemned to the eternal fire (katakrithésomenois eis to pur to aiónion) which will punish (kolasei) to the very end those delivered to it" (Epistle to Diognetus 10:7; written in the middle of the second century AD).
"Among those who had denied [Christ] was a woman of the name of Biblias. The devil, thinking that he had already swallowed her, and wishing to damn her still more by making her accuse falsely, brought her forth to punishment (kolasin), and employed force to constrain her, already feeble and spiritless, to utter accusations of atheism against us. But she, in the midst of the tortures, came again to a sound state of mind, and awoke as it were out of a deep sleep; for the temporary suffering (tés proskairou timorias) reminded her of the eternal punishment in Gehenna (tén aiónion en Geennéi kolasin), and she contradicted the accusers of Christians, saying, 'How can children be eaten by those who do not think it lawful to partake of the blood of even brute beasts?' And after this she confessed herself a Christian" (Epistle From the Church of Lyons and Vienna, 1.25; written in c. AD 177-178).
Compare with these earlier Jewish sources:
"The judgment of all who walk in such [wicked] ways will bring an abundance of afflictions (lrwb ngw`ym) at the hands of the angels of perdition (m'lky chbl), for eternal damnation (lshcht 'wlmym) in the wrath of God's furious vengeance, with terror and shame without end (lz`wtntsch wchrpt), with a humiliating destruction by fire in the darkness (`m klmt klh b-'sh mchshkym). For all eternity (qtsyhm), generation by generation (ldwrwtm), they will spend in bitter weeping (b-'bl) and harsh evils (ygwn wr`t) in dark abysses (b-hwywt chwshd) without any remnant nor rescue from destruction" (1 QS 4:11-14; the Qumran Community Rule was written in the late second century BC) "Put us to the test then, tyrant; and if you [i.e. Antiochus IV Epiphanes] take our lives for the sake of our religion, do not think you can harm us with your torments (basanizón). By our suffering and endurance (kakopatheias kai hupomonés) we shall obtain the prize of virtue and shall be with God, on whose account we suffer. But you, because of our foul murder, will suffer (karteréseis) at the hand of divine justice the everlasting torment by fire (aionión basanon dia puros) you deserve" (4 Maccabees 9:7-9; written in the first century AD).
"They [the Essenes] believe that every soul is immortal (psukhén pasan men aphtharton), but that only the souls of the righteous receive other bodies ... while those of the wicked are punished with an everlasting punishment (aidiói timória kolazesthai)....[The Sadducees] do not believe in an immortal soul and the punishments (timórias) and rewards in Hades" (Josephus, Bellum Judaicum, 163, 165; written in the laste first century AD).
Also the NWT rendering embodies an exegetical tradition going back to Russell and the Emphatic Diaglott. I could provide references indicating this.