Crib talk
Crib talk or crib speech is pre-sleep monologue made by toddlers while in bed. This starts somewhere around one-and-a-half years and usually ends by about two-and-a-half years of age, though children can continue longer. It consists of conversational discourse with turn-taking, often containing semantically and syntactically coherent question-answer sequences. It may contain word play and bits of song and nursery rhyme.
Crib talk has been found in deaf children in their early sign language. It also occurs in autistic children.