Hello. :)
I think the "two syllables ending in -n" is as much from surnames that have that form that have become popular as male names over the years as it is from Celtic names like
Kevin that accidentally had that pattern in the first place.
The "great PR" of the Irish is not something that started recently, at least in the USA. It goes back to around World War II or even a bit before. It comes from the Irish being the first "non-English" ethnic group in the USA to reach the "fourth generation" status. Most immigrants to the USA in the past wanted to give their kids "American" names to help them fit in and overcome prejudice. The Irish were no exception to this. But by the time the third or fourth generation in the USA is born, people become nostalgic about their "roots" and romanticize them, and start to search for names that reflect their ancestry. This started with the Irish back in the middle 20th century with girls' names like
Kathleen,
Maureen, and
Colleen --
Colleen actually being only a
word in
Ireland itself at that point; the idea of turning it into a name was strictly an American one. Ever since then each generation comes up with its own "Irish revival" names. You had
Kevin,
Sean, and
Brian in the late 20th century, and
Liam,
Connor, and
Finn more recently for boys.
Colleen gave way to
Meghan (also a psuedo-Irish name; Americans thought it was Irish, but it was really Welsh) and
Caitlin -- and of course then there are all the Irish surnames that Americans have adopted as given names, such as
Kelly,
Ryan,
Reagan,
Kennedy,
Nolan,
Braden,
Grady,
Donovan,
Rowan,
Shea,
Sullivan, etc.
The Welsh and to some extent the Gaelic Scots have benefited from the romanticization of Celtic names and culture that many Americans have bought into. And
Elinor's experience with the taxi driver is not unusual -- Americans will very often say "I am Scottish" or even "I am French" on the basis of having an ancestor from several generations ago who came from Scotland or
France. There are plenty of people in Europe who have great-grandparents who were from another European country, but they will very seldom use phrasing like that, since in Europe to say "I am French" means "I am a citizen of the country of
France" no matter what one's geneology is. But Americans, having such a short national history of their own, often completely romanticize their European ancestry in a way that would shock or amuse their actual great-great-grandparents who were probably happy to have left whatever country it was they immigrated from! :)
Italian-Americans have just reached the point of being far enough removed from their immigrant ancestry that they can feel "romantic" about Italian names, which is the reason names like
Gianna are so popular in states like New Jersey that have large Italian-American populations. In another decade or so, we'll probably have Polish Americans reviving Polish names in the same way.