Technical It turns out getting domain availability is harder than it should be. Several domain registrars provide APIs, but these are rate limited and slow. Finbarr figured out that you can just use a DNS lookup through a public nameserver like Google's to determine availability. This is critical to deliver the results quickly.
Story The idea came from a joke. Because Karen has such a common name, she never stood a chance at owning karencheng.com. She pledged that her future children would not be subject to the same fate- and she'd ensure this by making sure the domain is available before naming her child. Finbarr joked that there should be a website that automatically does this for you. Awesomebabyname.com was born.