It's actually what Kristin Chenoweth's voice teacher taught her. She made the mistake of telling Ellen about that when she was a guest one time, and then when Ellen put together "Ellen: the musical!", well, this was an obvious thing to include.

According to her autobiography, her hoohoo also tells the weather, thanks to a really improbable accident in which she broke her tailbone. (Apparently, if you're short, skinny, and female, your tailbone is closer to your hoohoo than it is for men. Who knew?)