What Does Aionios Really mean?
Aionios does not mean eternal... at least not all the time.
Translating from one language into another is never an exact science. Words have a semantic range, and often, we can find words with an overlap, but rarely does that mean two words from two different languages have the exact same meaning in all situations. That means we are making subjective decisions in our translations, and those translations sometimes need to be re-interrogated.
The English translation of Aionios into "eternal" is one of those cases.