Katie and the "nah"-ty word

Katie has picked up a new word/form of expression. She's recently started saying "Nah." This is usually accompanied by a nose crinkle and sometimes said with force. It was cute at first, like so many things are, but after a couple of days it started to wear thin. I don't know where she heard this because I don't think John and I started it. Boy, I never thought I would miss hearing her say "No."