infantile vs kid stuff

infantile

adj
  • Pertaining to infants. 

  • Childish; immature. 

kid stuff

noun
  • Something that is easy to do or easy to understand. 

  • Something done by, used by, or characteristic of immature people, especially children. 

How often have the words infantile and kid stuff occurred in a corpus of books? (source: Google Ngram Viewer )