No, Irish is not the name of a saint.
Saint Brendan the Navigator
There is no saint named Niamh. She is a mythical Irish character.
Patrick brought Christianity to the Irish.
Saint Cinnia was an Irish princess who was converted by Saint Patrick.
Saint Patrick is the best known of the Irish saints.
Saint Brendan
No but it is a variation of Mary
saint patrick
No. She is an Italian Saint. She was a disciple of St. Francis of Assisi.
There is a Rebecca, a matriarch from the Old Testament and there is a Saint Rebecca the Martyr who was martyred in the 3rd century in Alexandria, Egypt. Then there is St. Rafqa, sometimes called Rebecca, from Lebanon. None are from Ireland.
A good Irish saint, her story is at the link below: