You searched for: “paedology
pedology, paedology (s) (noun) (no pl)
Rare, the branch of biology, sociology, and psychiatry,regarding the study of the nature of children: Pedology is concerned with the child in his o her physical, mental, and social development.

Pedology involves infantile or childish speech that omits all but the principal words and substitutes easily pronounced sounds for more difficult ones, also known as "baby talk".