Yeah, if we were talking etymology, then aion would mean "to breathe" and aionios would mean "bone/spinal marrow," but that's not what we're talking about at all. Aion and Aionios are emphatically "limited duration," or "limited duration pertaining to_____(fill in the blank)" in every instance of Septuignt and Apostolic Greek. To argue it's usage in the Septuignt isn't an appeal to etymology since Greek goes considerably further back in time. Or on etymology we'd have to go with Aristotle that aionios means having always existed. Some say it's from aei, but aei is used 8 times in the New Testament and always of a limited duration in the New Testament. Aion also has "memory of man" or "age of man" for it's earliest definitions, but no one at these boards makes those arguments.
Macknight: (Scotch Presbyterian.) "These words being ambiguous, are always to be understood according to the nature and circumstances to which they are applied." He thinks the words sustain endless punishment, but adds: "At the same time I must be so candid as to acknowledge that the use of these terms, forever, eternal and everlasting, in other passages of Scripture, shows that they who understand these words in a limited sense, when applied to punishment, put no forced interpretation upon them.
Hanson cites Jones in his book as including "a good demon" in it's etymology. Nobody here uses these etymological arguments when asserting that aion and aionios are necessarily limited in scope and duration.
Eternity was completely unknown to the ancients according to Dr. Edward Beecher, Elhanan Winchester, and quite a few others.
In the Iliad and Odyssey Aión occurs thirteen times, as a noun, besides its occurrence as a participle in the sense of hearing, perceiving, understanding. Homer never uses it as signifying eternal duration. Priam to Hector says, "Thyself shall be deprived of pleasant aiónios" (life.) Andromache over dead Hector, "Husband thou hast perished from aiónios" (life or time.)
Dr. Beecher writes "But there is a case that excludes all possibility of doubt or evasion, in the Homeric Hymn of Mercury, vs. 42 and 119. Here aión is used to denote the marrow as the life of an animal, as Moses calls the blood the life. This is recognized by Cousins in his Homeric Lexicon. In this case to pierce the life (aión) of a turtle means to pierce the spinal cord. The idea of life is here exclusive of time or eternity." These are fair illustrations of Homer's use of the word.
Hesiod employs it twice: "To him (the married man) during aiónios (life) evil is constantly striving, etc. Ćschulus has the word nineteen times, after this manner: "This life (aión) seems long, etc. "Jupiter, king of the never-ceasing world." (aiónios apaustau.)
Pindar gives thirteen instances, such as "A long life produces the four virtues."(Ela de kai tessaras aretas ho makros aión.)
Sophocles nine times. "Endeavor to remain the same in mind as long as you live." Askei toiaute noun di aiónos menein. He also employs makraion five times, as long-enduring. The word long increases the force of aión, which would be impossible if it had the idea of eternity.
Empedocles, An earthly body deprived of happy life, (aiónios.)
It having clearly appeared that the noun is uniformly used to denote limited duration, and never to signify eternity, it is equally apparent that the adjective must mean the same. The noun sweetness gives its flavor to its adjective, sweet. The adjective long means precisely the same as the noun length. When sweet stands for acidity, and long represents brevity, aiónios can properly mean eternal, derived from aión, which represents limited duration. To say that Plato, the inventor of the word, has used the adjective to mean eternal, when neither he nor any of his predecessors ever used the noun to denote eternity, would be to charge one of the wisest of men with etymological stupidity. Has he been guilty of such folly? How does he use the word?
Plato's usage of the word is noted here: http://www.tentmaker.org/books/Aion_lim.html
Again, nobody's been using etymology to assert that aionios is always, consistently "a limited duration pertaining to_____(fill in the blank)." It's just the facts of Septuignt and Apostolic.