Final Update 16 February 2019

Im finally signing off on this but it has been great researching the Irish that could fit this song as I am learning the language and it has helped me a lot, with the process of looking up words in Irish dictionaries, finding out about the structure, pronunciation, and history of the language. It really is a beautiful language and such a shame that only some people in Ireland today speak it on a daily basis.

Final comments
It looks like Oonagh the German popstar (Senta-Sofia Delliponti)– in the green dress - made up this chorus using Tolkein's elvish languages which she sings in some of her songs. The other Celtic Woman singers in the song say that Oonagh is responsible for the chorus.

As she is german, it is difficult to even know if the words are pronounced as they should be ! Eg 'nugga' I have as nuk-kuh for the Irish word nuige which is not pronounced nuige, but changes to nuk-kuh (dont ask why !)

However, parts of the chorus as sang definitely are Irish and without a question of doubt Tír na nÓg is 100% from the Irish language. So I have used poetic license and a bit of reverse engineering to take Celtic Woman’s chorus and put it into what it could be if it had been written in an Irish more or less equivalent.

For this all to hang together, Sha-ta-co-ti-oh must be converted into a name and since this name does not exist, I take the poetic license and say that the faeries made it up and use it in their spell of enchantment.

In my interpretation, the faeires put a spell on the poor, young man with an elvin kiss, and then take him through the ancient mist to Tír na nÓg.

After all, who could possibly resist, the seduction of 5 beautiful wood nymphs, who are calling to you in a magical name that you are beautiful and handsome and to come with them to a special magical land which is far away from the troubles of the mortal world, and where he will find eternal bliss ?

So this apparently is a classical faerie tale straight out of celtic folklore. As such scenes are portrayed in Marion-Zimmer Bradley's the 'Mists of Avalon' of entry to the faerie world, that's why I quoted it as a reference source. The other source is a very old Irish-English dictionary which explains the pronunciaton and where I found Irish words that I couldnt find anywhere else which matched the meaning of the song and approximately matched the words used in the chorus by Celtic Woman and Oonagh.

My final source is Terre Celtiche where I found out that what I had suspected of the faerie seduction was correct:

"Along the lines of the fairy raptures of the Celtic tradition, today, like yesterday, some songs are written. The fairy sings with seductive words his call to the beautiful mortal inviting him to follow her in the Land of Youth (in Irish Gaelic Tír na nÓg): a wonderful island (which in the Arturian cycle takes the name of Avalon) or a great plain inside the prehistoric mounds, where the horses run, the women are beautiful, the orchards are lush, the music is sweet, the weather is eternally serene, where the Celtic warrior who dies heroically in battle is sure to be welcomed."

See my reference also to Avalon in the 'mists of Avalon' which is mentioned above by Terre Celtiche. It has some similarities to the tale in the song. Avalon is also cloaked in an ancient magical mist. There are faeries in the woods near Avalon. As the story goes.

Kevin (Merlin of Britain) succeeds Taliesin after his death. He is a horribly disfigured hunchback, having been burned in a fire as a child, but can sing like an angel. He becomes Morgaine's lover and later her worst enemy. Foreseeing the demise of pagan ways, he betrays Avalon. In an ultimate attempt to unite Christianity and Avalon, so Avalon will survive, he brings the Holy Grail to Camelot. To punish him for this atrocity, Morgaine sets up Nimue to seduce and then betray him, and wants to torture him to death as a traitor. But before the torture begins, Morgaine changes her mind and has him executed swiftly out of mercy, and at the same time, a bolt of lightning incinerates the Holy Oak of Avalon. Morgaine understands that Avalon is doomed.

Nimue enchants and seduces the Merlin of Britain. She seals his fate with a kiss completing her magical spell immediately after Kevin takes her maidenhood. This shows the power of a magical kiss. After that he is doomed and taken back to Avalon where he is executed.

Find the Terra Celtiche FB page and look for Celtic Otherworld.

I now have a job of translating some of the Irish on that site so I am very please to have been asked and can call on my new online Irish community throughout the world to help me as I learn the Irish language.

Some updates I did.

Update 15-February
Remove term gaelic as confuses with Scottish gaelic which is a different language. 'Irish' stands alone as an ancient celtic language.
My best attempt at the Irish pronunciation of the words in some cases doesn't equate with what is being sung in the song. Sciamh-ne instead of scum ne. Scum is not a word that would fit in this song but has an Irish equivalent. 'Sciamh' is the closest fit I could find but is pronounced skee-ah-v.
Ne is a possesive article and joined to the end of the adjective. Note Irish sentences invert compared with English: Saeta-Catia, sciamh-ne rhiabhanach=Saeta-Catia, beauty-our, handsome young man.

Update 13-February
Corrected gaelic pronunciation best attempt in chorus - will progressively update as I learn more of the Irish language

Update 11 February 2019

Some changes made to the chorus to break down its components and replace 'come with us....' to possibly 'come with me to' .... Tír na nÓg

Update 6 February 2019 - I will post more as I learn more : the roots of the chorus lie in an ancient language older than latin and the English language and at least 2000 years old !

- there are words missing for 'come with us' due to the metre of the song so 'nuige Tír na nÓg' is used instead which clearly implies 'come with us as far as Tír na nÓg' : so often in Irish words are omitted when 'everyone' knows it should be there.

 
My interpretation of the story in the song is that perhaps a young handsome man has chanced upon a clearing in an enchanted wood surrounded by 5 faeries who put a spell on him and then whisk him off to Tír na nÓg never to return to the land of mortals ! So the song is recounting the age old faery story of a mortal being seduced and abducted by faeries into the otherworld.

• Tír na nÓg - Land of the Youth: fabled land in Irish mythology where everyone is in paradise and all are young for ever and never die or grow old; they have everlasting youth, beauty, health, abundance and joy. Its inhabitants are the Tuath(a) Dé Danann, the Gods of pre-Christian Ireland.
• You bear the mark of my elven kiss: old English ‘Elven’ means from a female spirit, nymph or fairy – usually depicted as a beautiful maiden, inhabits rivers, woods, or other locations. A kiss from an elven maiden enchantress marks completion of a spell and seals the fate on the victim.

Sources
Various, and special mention to ‘The Mists of Avalon’ by Marion-Zimmer-Bradley 1983; which has vivid scenes of entry to the Faerie world from a clearance in the woods near Avalon, which is cloaked from the real world by magical, ancient mists. Also A Gaelic Dictionary in Two Parts 1 Gaelic, 2 English by RA Armstrong’ 1825. The world's first Gaelic-English dictionary.