In case I haven't mentioned it to you in person, the girls do have at least one secret twin word, a word they use that only exists in their personal lexicon. I'm sure there are others bubbling up but I have only noticed this one clear word, "Ni-noh". They say it when they want to trade toys. I know if I hear it from another room that I will look in and find them swapping plates or push-toys or spoons or whatever. I will be on the lookout for other secret words.