When i lived in England, in South Yorkshire, i knew quite a few Nigels. And nearly every one of them was known to his friends as Nig (rhymes with ridge, not with dig).
One woman’s name that i have never seen here in the US is Bronwyn (or the alternate spellings, like Bronwen). I believe it’s of Welsh or Scottish origin, and i knew quite a few women with this name when i lived in Australia.
I think my name qualifies – I’ve not heard of anyone in the US with it, but it’s not that uncomon in England.
What? Wat? Never heard it. And I used to live in England!
Funnily enough, Sue Townsend, the author of the Adrian Mole series of books, gave Adrian an American friend in the first book. His name? Hamish Mancini. I thought to myself, “That’s the most affected name I’ve ever heard.” She might as well had called him Lance Uppercut or Brent Harbison.
I would add this one: Antony. We have Anthony here.
I knew a few Rolands as a kid and a character on Grange Hill had the name (as did a certain stuffed rat puppet). I’ve only known one American with the name, and he’s actually Filipino.
Jeremy is much more popular in the UK, I’d say, than over here. I only met Jeremys in college. Loads of Jeremys roaming the countryside when I was a kid.
Also, Maurice - which in the UK is pronounced “Morris.” Not common, but not unheard of either. The homophone is spelled “Morris,” while the homonym is pronounced “Maw-reece” on the left side of the pond.
A really ancient one from some old books is “Dickon.” No American kid was ever given that name. Ditto with “Beverly,” which was once a bloke’s name.
mhendo, I’ve known at least two Browyns in the US, who both were insufferable. Hopefully the UK versions are better than the ones I’ve met over here. Incidentally, the Nigels I knew were “Nige,” rhyming with Mary J. Blige (this was in the Midlands and East Anglia).
I think the nicknames are much more interesting. When I was a preteen the -az and -azza nicknames were popular, so you had Baz, Jaz, Gaz, Chaz, Shaz, etc. If you were little and tough you were called “Titch,” which I still think is a great nickname…
Titchy Hollow… I like the ring of that.
That’s often just a matter of pronunciation, not spelling.
In the UK, Anthony is often pronounced Antony. One of our family members has the name Anthony, and my mother, who is originally from England, pronounces it Antony.
Yeah - where the hell did ‘wat’ come from?!
The only one I can think of was Wat Tyler, and he died in 1381. Short for Walter, apparently.
Hmm, and here I am on the dope for at least two years or so
Declan
I know it’s boys’ names, but I have never encountered an American Gemma. They’re a dime a dozen in the UK.
I have heard Siobhan among the the 20 year old set in the States, but I never heard it in America with anyone in my age range (30s). It was common enough in my childhood that I knew that the name linked up with “Shah-von.” (One of the girls in Bananarama was named Siobhan.)
Hillary and Nora (as previously mentioned) are known names in the UK, but I’ve met few Americans with those names (Clinton and Jones nonwithstanding).
Similar in the UK, where the name’s recently become popular.
Stephen as opposed to Steven?
It’s been reasonably popular in the Celtic Fringes for a few decades now. Caitlin seems very popular for baby girls these days. Is Catriona known in the US at all?
rhymed with ridge? Im used to Nig being pronounced the same as it is in the river Niger.
I know a male Erin! He’s Canadian. There, now you’ve heard of another. 
And now that the only thing I could have contributed to the thread has been contributed, that’s all!
If you’re still on Irish/Celtic names, how about Dermot (Diarmuid)?
sin
Unless they’re Angelic.
Heh. :o (I think that means: Here, I will give you a blowjob to make up for my crass mistake.)
For some reason, I don’t like the name Steven, but I don’t mind Stephen. I briefly dated a Dubliner named Stephen, and when he first introduced himself, I was turned off by his name, but when I figured out that he spelled it with a PH, I liked it. 
Maybe it’s because there was a bully named Steven in my grade at elementary school. Or I just don’t like the letter V. Or maybe it’s just because I’m weird.
Must be a Doncaster thing, i guess.
I have an addition to this – I know a little GIRL name Aaron!
I have known several people named Iain - some of them pronounced it “ee-an”, some “y-eye-an”
That reminds me…
When i was at university back in Australia, we frequently had American students who would come and spend a semester on exchange. In one of my classes, there was a female student named Gavin. I’d never heard of Gavin as a woman’s name.