Teach your baby the sign for the word play in baby sign language with the following description and video.
Form the hands into the signed letter Y. Shake the hands back and forth in front of the chest.
Acredolo, Linda & Susan Goodwyn. 2009. Baby signs: How to talk with your baby before your baby can talk, 3rd edn. New York: McGraw Hill.
Beyer, Monica. 2006. Baby talk: A guide to using basic sign language to communicate with your baby. New York: Jeremy P. Tarcher/Penguin.