The God who owned the hill upon which stood the Holy Well of All Knowledge.
This is the well that BOANN managed to upset so much that it chased her down the hill and boiled into the River Boyne. As a matter of course FINTAN the Salmon of Knowledge went whooshing into the river as well. Or the well as river.
NECHTAN gnashed his teeth and took to nibbling the hazel nuts of knowledge, which only made him sadder but wiser. He knows he is now just another crazy nut.