The AoE (Apple of Enlightment) is not a thing nor a legend passed down from generation to generation. The AoE is an Idea. The AoE has much to do with Mother 1. It was Passed from the first game to the second. If in fact Giegue is Giygas the AoE was started with the creation of Giegue.

When Giegue was born to it's alien parents, it was not the Cosmic Destroyer... Or it didn't know it was. AoE (the idea) was created and predicted to George warning him. Thus George became the Apple of Enlightment. We all understand why "Enlightment" is used. Enlightment is a term meaning higher than the state of mind. A sentance we might use enlightment is would be: God is enlightened. Now you get the idea. Why apple is used I will try to decribe. Even though I am not so sure myself.

An apple is a common fruit. The color it is most known for is red, and it's seeds are in the center. Because the apple is a common fruit this means the AoE is a common thing. The AoE exists every Millenium, when ever Giygas appears. One millenium is a short time in real legends that have been passed down in different countrys. Red, the color of an apple is a primary color. This means the AoE is needed for all things to work, and keep Giygas from winning. Last, because the apple's seeds are in the center. This means that only the people who are ancestors of George, Giegue, or people who are helping the chosen ones can hear the "idea" (AoE) or write it for that matter. Now back to the theory.

George recieved this "idea" and wrote it in his journal. This is why only people who have PSI or who are helping the people with PSI can read or hear it. When Maria drove Giegue to put her in Magicant he bacme the Cosmic Destroyer. This is when the sound stone was created. This is why only the chosen one can hear the song of Maria and enter Magicant. When Maria heard her song and left Magicant her song was again spread across the earth and Magicant was closed into the Sound Stone.

When Giegue was destoryed by the chosen ones, three boys and one girl, he was forced to insanity. This is when he became obsessed with power. The AoE predicts that every millenium ancestors of the chosen ones will defeat Giygas. I think in some way Giygas was a term used in Scarabia (in the game) which means "Total Destroyer".