- First born son named after his father's father
- Second born son named after his mother's father
- Third born son named after his father
- Fourth born son named after his father's oldest brother
- Fifth born son named after his father's 2nd oldest brother
or his mother's oldest brother
- First born daughter named after her mother's mother
- Second born daughter named after her father's mother
- Third born daughter named after her mother
- Fourth born daughter named after her mother's oldest sister
- Fifth born daughter named after her mother's 2nd oldest sister
or her father's oldest sister
This bit of knowledge can be immensely helpful; for instance I know from church records that my 3rd great grandfather Michael Hore married Mary Travers in Rathvilly, Carlow in 1814. I was given copies of research done by the Carlow Genealogy Project Center (now defunct) by the cousin who commissioned it, sadly now also gone. Their report claimed that Michael's father was also named Michael. I can't imagine why they believed this. Old Irish marriage records did not include parent's names. I've seen the church record and no, there is no father's name included. So where could it have come from? Needless to say I'm very skeptical. The first two sons of this family were named Patrick and John, using the above pattern, I can see it's much more likely that Patrick was Michael's father. Not proof by any means, but a distinct possibility. The third born son was indeed named Michael after his father, so it would seem they did follow the pattern in naming their children.
I found a baptism for Maria Travers in the nearby parish of Castledermot in 1794, parents John Travers and Margaret Lawler. This seems to fit the pattern,the second son was named John, and would lead me to believe the first Hore daughter would be named Margaret, instead it was Winifred. But wait, looking at the 1865 census of New York State, I found that Mary Travers Hore told the census taker she had 8 children, not the 7 listed in church records, it just might be that the "missing" child, who appears to have been the firstborn of this marriage, was named Margaret. Another example why it pays to collect every bit of information you can find on an individual.
I've also found that just as some surnames are more common in certain areas than others, so too are some given names. David is not a name that springs to mind in relation to 19th century Irish Catholics, but there was a cluster of them in County Waterford, and Andrew was more common in Tipperary.
In closing, the naming pattern is important to consider, but it's not chiseled in stone. There are cases where it wasn't strictly followed, and there may be undiscovered children or circumstances the researcher is unaware of. I puzzled over why it was, the last son of Cornelius Ryan bore his name and not his 3rd son. Then I found the baptismal records of the 3rd son, Thomas Ryan. Turns out Thomas had a twin who died shortly after baptism, care to guess his name?