What is a Damfoo?

So we were having family night tonight. (We usually have it Monday night, but my Honey will be on travel.) We have just finished up and are getting ready to put the kids in bed. My sweet son is pleading with me to read him the same book for the fifth time, today. I was looking to distract him and put the book on my head and told him it was a hat. He thought it was mildly funny. Not the Wild Child, she thought it was hilarious! In fact she said "You look like a Damfoo." Of course, I have to ask what a "Damfoo" is. Her reply, "You know a Daaam Foooo, that's what you are if you have a book on your head!" I was a little slow, I am sure the rest of you figured it out a lot faster than I did. All of the sudden the penny drops for me. "Oh! Hey Wild Child that first word is a swear word and we don't say it. OK?" With bright smile and a twinkle in her eye she says while nodding her head, "I do mom, I swear. I really do!" Oh Hell, what am going to do now.