baby boy vs youngster

baby boy

noun
  • A very young male human being, from birth to a couple of years old. 

  • A term of endearment for a man. 

  • A man who is immature or infantile. 

youngster

noun
  • A young person. 

How often have the words baby boy and youngster occurred in a corpus of books? (source: Google Ngram Viewer )