Still, I looked it up on an online dictionary (don’t have one of my own), and the only other way to say sun that comes up is "taiyou". Now, Tidus’ name is something like "Taidasu", but that’s not enough evidence to claim anything. Why? The "tai" in "taiyou" (and the common sound between taiyou and taidasu) means great, fat, or thick. That has nothing to do with the sun.
Someone like rezo who knows more than me, feel free to correct me if I’m wrong, but I’m really not buying the connection at all.
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Here’s some from FF9.
Vivi’s name in Japanese is "Bibi," and one of the first things Puck says to Vivi as they’re climbing over the rooftops is "bibina yo!" which is a Japanese play on Vivi’s name that translates to "Don’t be a wuss!" or "don’t be such a ‘fraidy-cat!" Since Vivi was often struggling to overcome being afraid of everything, the word "bibiru" and the name "bibi" could very well play off each other.
Another thing is that the translated name "Vivi" can also mean "I live" in Latin, and could apply to Vivi, too.