I read somewhere that the Gaia cliff was mistranslated into gaeas.
It was, but the planet is always referred to as "The Planet", it did not have a name in the original game. The cliff is named Gaia as far as I am aware.
Gaia Cliff is not the same as "Cliff of Planet Gaia", so it depends how the name is meant:
Gaea's Cliff > ガイアの絶壁 > Gaia Cliff
That seems to be a cliff called Gaia?
As far as I can see, nowhere else in the game is Gaia even mentioned. Then again, Gaia and Terra are used in FF9 as names for planets, and it is at least possible. I will check.