Sister Language

I have heard it said that sometimes twins create their own language that only they can understand.  My two girls did this over the summer in 2012!!!  If you were to overhear them these days, you would hear they talking about "mew-bits" and "curbi-sabs" and "sunion" and "cute-lets" and "grunion" and "curb" and "pasqua" ... and may combinations of these like "sunion grunion curb." They often use these words to refer to cute animals.  A "mew-bit" is absolutely a kitty, ... and a "grunion" is definitely a bird, ... and a "pasqua" is any moth or butterfly, ... and a "cute-let" is absolutely any cute animal, but the rest of them are a mystery to me.  And if I ask them what a word means, they get fairly offended that I am intruding on their sister space.  :)