Aiden is a spectacular name success story--in fact, if all its various spellings were added together, it would now be the top boys' name in the country. This year, Aiden cracked the Top 10--the Aiden spelling has far outperformed the traditional Irish Aidan and has now become the accepted version, after spawning a pack of popular rhyming offshoots such as Brayden and Kaden.
Aidan was originally a pet form of the Irish name Aodh (pronounced 'ee'), who was the old Celtic god of the sun and fire. St. Aidan was a famous seventh cenury Irish saint, noted for his kindness and generosity and for spreading Christianity. Americans first noticed it via actor Aidan Quinn; the Aiden spelling was used by actress Tracey Gold and Rod Stewart for their sons.
Aiden/Aidan is just beginning to wander into the girls' side of the gender divide, but with so many little boys given the trendy Aiden name today -- it's number one in some states -- we don't recommend it for girls.