As to Caitlin=Katelyn. I have also known a Siobhan...only they spelled her name Shevaughn. I think it is the trouble that most American English speakers (myself included) have with Irish and Gaelic spellings. We are just so far and away from the Isles, and there is so little call for learning those languages that it is simply too foreign. In the States, we're all hustling to learn Spanish, as that is the up and coming second language here.
And if anyone names their baby boy "Percy" here in the States, they had best also send him to Karate lessons. For sure, he's going to get his butt kicked at least some.
My honey is a brown belt (one test away from black) mostly for the reason that his last name is "Grossman", and he is not large in stature. (I.E.: butt kicking was a way of life growing up).