mdtauk
Member
I don't recall a line in the game that specifically mentioned that was the origin of the Master Sword. I just interpreted it as the Goddess Sword as being returned to its original state.
If I'm wrong, feel free to correct me.
A legend that will be forged by your own hand
Master, now that it has been tempered by the last of the sacred flames, your
blade has finally revealed its true form. You now hold the Master Sword.
I also think it was explicitly stated that the story was intended to be the origin of the Master Sword.