Here is some information which may be relevant and interesting. Having read the question earlier, I spoke to my 92 year old father later today about this subject of Catholic baptisms in Ireland during the penal laws (anti-Catholic laws) and we both agreed that many of them were probably carried out in private settings and not documented, especially with lower classes of people. He provided me with the text below which he copied word-for-word years ago during a visit to St Michan's church. This text was displayed at the entrance to the church. I am not sure if this text is still on display at the church. I have highlighted in bold a section relevant to the subject of baptisms.
St MICHAN AND THE CHURCHES DEDICATED TO HIM
(Copy of a document found under the altar of St Michan’s Church, Halston St. when it was being renovated c. 1990. It presumably dates from the foundation of the church in the late 18th century. It outlines the story of St Michan and of the churches and religious houses established in the area.)
Who St Michan was, has, until recently, been a mystery to ecclesiastical historians. The old Irish name (Glasmocanogue) of the street now called Constitution Hill, gives a clue to the mystery. Glasmacanogue is the boundary stream of the district that was under the spiritual care of Saint MoChanóg, namely St Michan.
He was the eldest son of the prince of Brecknock in Wales and lived in the fifth century. He founded the cill or church of Cill mo Chanóg (now Kilmacanoge in Co Wicklow) and his brother -- Mocaróg founded the cill in Delgany. It seems that, having founded the cill in Kilmacanoge, he then came to Dublin and set up a hostel in the Stoneybatter area. St Michan is mentioned in “A Calendar of Irish Saints” as Michan of Cill Michan in Atha Cliath (Michan of the Church of Michan in Dublin) and his feast is 25th August. In fact, his father, the prince of Brecknock in Wales, was said to have been an Irishman. After Michan set up his cill in Dublin, he returned to his native Wales and was slain in 496.
Michan’s cill or religious house continued for several centuries and in 1096 the foundation of the Cathedral of St Michan was laid by the then bishop. The church remained a cathedral for only a short time – until Christchurch became the cathedral in 1121. Archbishop Laurence O’Toole (1161) introduced Regular Canons into the cathedral to live in communities. In support of the Canons he granted various churches, with their tithes, among which was St Michan’s (1178).
The Protestant government took over the Church of St Michan (in Church St.) in 1540 and the Catholic priests had to find new ways of providing the sacraments to their faithful. They had to resort to the back streets for those purposes. St Michan’s mass-house was in a back room of a house and became the first parish chapel recorded in penal times. The sacraments continued to be available to the people of the area through the penal times and limited Catholic education was provided for boys and girls. Teresa Mullaly founded Georges Hill where the Presentation Sisters continue their work to this day.
In 1704, the old building at the corner of Bull Lane was transformed into a chapel. The Novena of Grace in honour of St Francis Xavier was started in this chapel by the Jesuits in 1712.
The Irish name for Michan is Mo-Chan-Óg; the Mo (my) and Óg (little) usually added to saints’ names as terms of affection and Can was the surname. In Welsh, the Mo is rendered My and so, in the name Michan we have the Welsh pronunciation of My Can.
Note added by S.O’Connor: The derivation of “Michan” would seem to be more complicated than suggested here. The Welsh equivalent of the Irish mo is fy, which is pronounced vo, the vowel sound being exactly the same as that in the Irish mo. The adjustment of the name would, therefore, seem to have resulted from a misconception as to how the vowel sound y is pronounced in Welsh.
