Not a lot is known about NYU, but my friend and student, Andrea Pezzati, has done some research on it and I would like to post what he has found. Andrea is from Italy and he is currently studying more on this subject among others.
NYU
Written by Andrea Pezzati
The Druids knew of the existence of a fifth element called NYU in Gaul but better known by its Welsh name of NWYWRE. Nwywre was symbolized by the serpent and was a universal symbol already familiar to us from the statues of the Pharaohs, who were thought to represent the divinity on earth.
According to Moreau, this element represents the creative power of the material world, the creative principle that links together Sky and Earth. The union between NWYWRE and the four elements created life, movement and spirit.
The Welsh bards said that NWYWRE is the smallest of the smallest yet also that it is bigger than the world because it is subtleness and power itself all rolled into one.
For the Druids,the NWYWRE is the thread that links together the human world with the divine one...the NWYWRE is all of this and was symbolized by the snake...in India was named Akasha, in Egypt...NUN and in Greece...ETHER.....The ancient welsh druids called themselves Nadredd (serpents) and during initiation, they would yell..."I am a Druid. I am a Serpent".
NWYWRE (also spelled Nwyre) is also related with the tales of the cauldron of Ceridwen...i.e....the NWYWRE was the essence of the three drops (from this cauldron) drank by Gwion (Gwyon) Bach that gave him knowledge,wisdom and power. Gwion Bach is the name for the young Taliesin, the well known welsh bard,shaman and druid.
I have found another little thing about the Nyu...also known as Akasha. It is a short quotation from the original text of the Barddas (as published in the 1794 by Iolo Morganwg) followed by a comment on it made by Philip Carr-Gomm,the current chosen head of the "Order of Bards,Ovates,and Druids",and a well known author of books on druidism.
--------------------
Iolo Morganwg from Barddas
"There are five elements: earth,water,air,fire and nyv; and the nyv is God,from Whom are all life and orderly motion."
Philip Carr-Gomm
"Iolo Morganwg invented much material,but he undeniably had access to traditional sources too. In this quotation,which he claimed as ancient and authentic,we learn of a fifth element,known as nyv (Nyv is a variant form of Nwyvre,Nwyvre being defined as a fine ethereal fluid in swift motion). Nwyvre,as we know already is the life-force that flows through all things,and here it is being equated with that element more commonly referred to in the Western Tradition as Spirit or Aether. In Barddas,Iolo refers to Nwyvre as "every animation and life, and every strength,understanding,and knowledge,and the same is God,without Whom there can be no life and vitality".
Sources: "La Tradition magique des Celtes " by Marc Questin
Myths and Legends of the Celtic Race by T.W.Rolleston
Celtic Lore by Ward Rutherford
Il Vischio e la Quercia by Riccardo Taraglio
Iolo Morganwg from Barddas
Philip Carr-Gomm
