My sister has 5 kids and they each have their own "special words".
I have no idea where they came up with these either
lizard - Galivamp
Aunt Susie - Aunt Shmo
socks - ki's (like eyes with a k sound)
This is coming from a proud Aunt. These words are now part of my great-nephews/nieces vocabulary. I know there are more, but I can't think of them right now.