Hermeneutics relies on several critical factors for interpretation. Off the top of my head, I’d include
• Other specific scriptures – What other scriptures are relevant to the passage in question?
• Context within the immediate scriptures – What is the subject and what are the other words being used in the passage?
• Intellectual trajectory – What preparatory stages lead up to and what conclusions follow the passage in question?
• Semantic range – What other writings use a specified word, how do they differ in context, and what’s the etymology of the specified word?
• Linguistic analysis – What are the historical grammatical or idiomatic norms used?
• Historical interpretations – what are the historical range of interpretations and references for a passage, including other major Bible translations and recently discovered manuscripts?
• Opinions of experts – how do recognized experts and commentaries address the passage in question?
• Archaeology – What recent archaeological discoveries impact an interpretation?
• Logic - What logic is available to build or falsify a case for an interpretation?
Some of these can overlap, and I’m sure I’ve forgotten some other critical factors.
The word is derived from aión, SG 165 (similar to eon in English), which reports 165 occurrences in the New Testament.
In context, I looked up Titus 1 in the online Greek interlinear to confirm the word being used as aiōniou (SG 166):
https://biblehub.com/interlinear/titus/1.htm
Then, I looked up the word, αἰωνίων (aiōniōn) in my recently purchased BDAG (my wallet is still in shock) and found an entry under αἰώνιος (aiónios), which reads: “1. pert. To a long period of time, long ago . . . 2 Ti 1:9, Tit 1:2 (in these last pass., the prep. bears the semantic content of priority . . .”
Okay, but not entirely understanding “the preposition bears the semantic content of priority,” I looked at 2 Timothy 1:9 to get another example, where it reads in part
. . . and grace having been given us in Christ Jesus before time
eternal (aiōniōn) . . .
https://biblehub.com/interlinear/2_timothy/1.htm
Again, I would ask, "Priority over what or is this a form of emphasis?"
So, logically, I'd conclude that Paul would not have added the words "before time" in his letter to Timothy as a qualifier if aiōniōn wasn't a grammatically compatible word for eternity/eternal.
This context then raises the question of whether the "grace having been given us" should be interpreted corporately or individually, and whether Paul meant that this grace is applied specifically to the righteous saints of old, which is way beyond the scope of the question.
I hope this helps.