“The word aidios (not aionios) was in universal use among the non-Christian Greek Jews of our Savior’s day, to convey the idea of eternal duration, and was used by them to teach endless punishment.
Jesus never allowed himself to use it in connection with punishment, nor did any of His disciples but one, and he but once, and then carefully and expressly limited its meaning. Can demonstration go further than this to show that Jesus carefully avoided the phraseology by which His contemporaries described the doctrine of endless punishment? Jesus never adopted the language of His day on this subject. Their language was aidios timoria, endless torment. His language was aionion kolasin, age-lasting correction. They described unending ruin, He, discipline, resulting in reformation.”
This is taken from this article on the Greek word aion. Please go to the end of the page and look under “appendix”.