Other forms: Aiden, Ayden, Edan
At the moment, Aidan is sitting at #115 in the US. Spelled Aiden, it's number #10. It is currently suffering from a condition I like to call "overkill". Which is a shame, really.
Aidan comes from Aodhán, a diminutive of of Aodh which means "fire". Aodh is the name of of more than a few characters in Irish mythology, and even of a few High Kings. Aidan itself is the name of two Saints, countless characters on TV and in literature, and even some actors, most notably Aidan Turner who played vampire Mitchell on "Being Human" and recently Kili in "The Hobbit", Aidan Quinn, who is Irish-American, and Aidan Gillen, who is currently playing Petyr "Littlefinger" Baelish on "Game of Thrones."
One of the aforementioned Saints is St. Aidan of Lindisfarne, also known as the "Apostle of Northumbria". He was born in Ireland, and that is all that is really known about him, aside from that fact that he was a monk in a monastery on the island of Iona. He eventually founded a cathedral on the island of Lindisfarne, and is credited with bringing Christianity to Northumbria, a Kingdom of the Angles. It is today Northern England, and South-East Scotland.
It's not just us Americans that have fallen in love with it; in England and Wales, it's #101, and in its homeland it ranked #40 (#43 for Northern Ireland).