There's something they really used to get about nailing a level of mysteriousness in old titles that's just not replicated.

"Chrono" is an adjective that vaguely relates to time, and an object called a "Chrono Trigger" sounds like a curious time-related artifact. Notably, there's a layer there, the name isn't "Time Artifact"
"Final Fantasy" evokes a strong feeling with the word "Final", and has nice alliteration.
"Legend of Mana" is using all normal words, but Mana is such a fantasy concept it could mean a lot of things.
Drakengard is a made-up word, but it's memorable for being related to known words - "Dragon Guard".

But:
Bravely Default, while trying to push the two main game mechanics, shoves an adverb against a non-verb being used as a verb, and evokes no conceptual idea of the world or story.
Diofield is just a made-up word, and inclusion of the term "Field" is not promising.
Even if "Octopath" is going for something coy with the "8" relevance, and the 8-letter word containing the protagonists' initials, it's another made-up word, and "Traveler" is more over-focused on the characters than the journey/world.