I was brought up in Ireland. I thought I was pretty much familiar with Irish popular culture, particularly the aspects of it absorbed into my own family. But I didn't know this.
Angus Baxter in "In Search of Your British and Irish Roots" describes a pattern that was popular in England in the 1700-1875 period:
- The first son was named after the father's father
- The second son was named after the mother's father
- The third son was named after the father
- The fourth son was named after the father's eldest brother
- The first daughter after the mother's mother
- The second daughter after the father's mother
- The third daughter after the mother
- The fourth daughter after the mother's eldest sister
- John Harbison, (b. c. 1740)
- William Harbison (b. 1780)
- John Harbison (b. 1809)
- William John Harbison (b. 1854)
- John Henry Harbison (b. 1885)
The rule predicts alternation in given names along this line. You see this, for example, also in the kings of Denmark, all the way from 1534 up to the present day.
John b. 1809 had 7 daughters before he had a son, and so William John might have been an effort to cram 2 names into 1, because he was running out of time. In fact, most of my ancestors did not have middle names until the mid-19th century.
Anyway, as is obvious, we can predict the grandfather of William (b. 1780) was also William, and I have a candidate. More of this anon.