Most of it is from D&D actually, especially the misnamed monsters. Bahamut in Sumerian culture is a whale like beast but in D&D, Bahamut is a dragon and Sakaguchi has said they took the idea of Bahamut from D&D. Same with the White Mage weapon pool. Sakaguchi was actually asked this question at PAX recently and he said the staff borrowed liberally from other sources, in fact many of the monsters were renamed or changed/removed when the game was released in the West due to fears of lawsuits.

As for the Red Triangle for White Mages, it was most likely created to add contrasting color to the character sprite as opposed to some deep culture meaning.

I will give more info tomorrow when I have more time.