babyish

adj

1. Like or suitable for a baby or a young child; childish

   “For a young man, he has the most babyish voice I've heard.”

   “Clothes like these are too babyish for a child his age.”

   “As soon as the King and the rest of the hunting party had set off, she began making a tour of the whole castle and asking questions, but all in such an innocent, babyish way that no one could suspect her of any secret design.”