Fòram na Gàidhlig

Does anybody know about Fèill Eoin Ròid?

I'm trying to tr*nsl*t* "CUMHA CHOIRE AN EASA" le Iain MacAoidh (An Piobaire Dall).
And here I see "Fèill Eoin Ròid":

Is mi aig bràigh an Alltain Riabhaich
Ag iarraidh gu Bealach na Fèithe,
Far am bi damh dearg na cròice
Mu Fèill Eoin Ròid a' dol 'san dàmhair.

Am Faclair Beag says that it means "Feast of St John of the Rood (14th September)".
But I cannot find anything about the Feast; I know that the same day is the Day of Holy Rood / Holy Cross.
And also I saw the rood screens, with the Cross and the figures of St. Virgin and St. John the Evangelist.
Is this the same John and what do you know about his Feast?

St John of the Rood seems a funny way to tr*nsl*t* the name of the saint who is more commonly called St John of the Cross. He was a Spanish mystic in the 16th century. However, his feast day is 14 December, not 14 September. It sounds like these two feasts have been erroneously combined on AFB.

John of the Cross is best known for his work "The Dark Night of the Soul". He's also a Doctor of the Church. I don't know anything in particular about how his feast day is or has been celebrated.