John Simcox mentioned getting an 1880 book by interlibrary loan called "Aion-Aionios" in a recent comment. I have that book -- and now you can get a copy, too.
The Greek Word Aion-Aionios, Translated in the Holy Bible, Shown to Denote Limited Duration by Rev. John Wesley Hanson, A. M.
Hanson was a demominationally-popular writer. But why care about this subject? To show that "eternal punishment," that is, "aionian" punishment did not mean "ceaseless, without end" but a period of time applicable to that being discussed. He cites examples of "everlasting" or "eternal" (so translated) events that have, in fact, ended.