Idioglossia

Idioglossia is when a person creates their own secret language that only they and maybe a few other people can understand. It's like having your own special code that no one else knows. It's kind of like a secret club language that only certain people can understand. It is like when you make up your own word or use a mix of different languages to communicate with your friends, but only you and your friends can understand it. Some twins or siblings might develop their own special language that only they can use to communicate with each other, which is an example of idioglossia.