Minor nitpick. Of course, this is obvious to you, I know, but I'm saying it anyway for the record :-)
Approximately no one really names children "to fit into a trend" or because they really think "it's cool to be Irish (or Welsh or whatever ethnicity)." People in the same cultural time and place tend to share tastes - naturally & logically, if somewhat mysteriously. Irish-sounding names are like that in much of the US lately. When someone likes and uses an Irish or Irish-sounding name, they do it knowing it sounds fashionable; but that's not really their reason for using it, I don't think. I think they genuinely like the names, for reasons they can't explain.
So I take some exception to your tone of disdain for people who like and use Irish and Irish-sounding names, although in general they're not my thing..
I mean, I first started following name trends on the internet a couple years ago, and I thought my tastes must be so "different" -- but then I found out my favorites were actually pretty popular, and often the people who liked one, liked many of the others too. There's no way I could have been intentionally following a trend, because I'm not the most culturally in-touch person on the planet, let's just say. But it turned out I liked a lot of fashionable names that I hadn't heard anywhere for years prior to looking at name boards.
- chazda