Happy St. Paddy's Day!
Instead of listing tons of Irish names, which can already be found all over the internet, in varying degrees of accuracy, I've decided to focus on Irish names that already made it into everyday American usage.
For some reason, Irish names seem to hold a special fascination in the baby-naming world, and it's nothing new! Every generation has its imports, and I'd wager that Sean & Caitlin got just as many strange looks a few short decades ago as Declan & Aisling do today.
(yes, most of these names have existed for hundreds of years; this is when they gained widespread modern use in the U.S.)
Duane (via surname, Ó Dubhán)
Colleen (not a name in Ireland, just a word, cáilín)
Tyrone (an Irish county, not usually a name)
Kerry (another Irish county)
Shannon (yet another place-name, this time a river)
Ryan (via surname, Ó Riáin)
Casey (via surname, Ó Cathasaigh)
Erin (poetic name for Ireland, Eireann)
Tara (another place-name, Teamhair)
Cody (via surname, Mac Oda)
Riley (via surname, Ó Reilly)
Cassidy (via surname, Ó Caiside)
Brayden (via surname, Ó Bradáin)
Brady (via surname, Ó Brádaigh)
Nolan (via surname, Ó Nualláin)
Donovan (via surname, Ó Donndubháin)
Kennedy (via surname, Ó Cinnede)
Special mention goes to Patrick & Molly--although they are generally held as the epitome of all things Irish, both were actually used in English first!