Greek scholar William Barclay wrote concerning kolasis aionion (age-during corrective chastisement) in Matthew 25:46
“The Greek word for punishment is kolasis, which was not originally an ethical word at all. It originally meant the pruning of trees to make them grow better. There is no instance in Greek secular literature where kolasis does not mean remedial punishment. It is a simple fact that in Greek kolasis always means remedial punishment. God’s punishment is always for man’s cure.”
See what other Greek scholars say about it too.
AN ANALYTICAL STUDY OF WORDS – Louis Abbott
Fifteen literally translated (not interpretively translated) Bibles that reveal what God will do with the sinners in Matthew 25:46
Concordant Literal, Young’s literal, Wilson’s Emphatic Diaglott, Rotherham’s Emphasized, Scarlett’s, J.W. Hanson’s New Covenant, Twentieth Century, Ferrar Fenton, The Western New Testament, Weymouth’s (unedited), Clementson’s, The New Testament of our Lord and Savior Jesus Anointed, The Restoration of Original Sacred Name Bible, Bullinger’s Companion Bible margins, Jonathan Mitchell’s translation (2010).
Regarding the meaning of aionios, many Greek scholars agree with John Wesley Hanson.
AIÓN – AIÓNIOS
Dean Hough wrote “The definition given in THE VOCABULARY OF THE GREEK TESTAMENT (edited by James Hope Moulton and George Milligan) is helpful. Concerning aionios we read, “In general, the word depicts that of which the horizon is not in view . . .” (p.16). If the horizon of the extermination spoken of by Paul in 2 Thessalonians 1:9 is simply not in view, then we can see that what Paul says in 1 Corinthians 15:22 can truly occur. The same all who are dying in Adam, which includes some who incur eonian extermination, can indeed eventually be vivified in Christ.
The Bible, in fact, does not speak of judgment and condemnation, death and destruction, hades and Gehenna, or any of these serious consequences of sin, as unending. It may refer to them as not having the end in view, but none of these fearful works of God can keep Him from achieving His will (1Tim.2:4); reconciling all through the blood of Christ’s cross (Col.1:20, and becoming All in all (1 Cor.15:28).”