DD8 did this all the time when she was that age. She had her own language practically. she had a speech delay and we had to work to get her to use real language and not her made up language. she had her own name for everything. It was neat but she also had articulation problems so the combination of that and "anna language" (as we all called it in the house) made it so people couldn't understand 90% of what she was saying.
She didn't seem to mind.
She was out of speech therapy by gr K. She is still very imaginative and plays with language and words a lot.
