preemie vs suckling

preemie

noun
  • A baby that has been born prematurely 

suckling

noun
  • An infant that is still being breastfed (being suckled) by its mother. 

  • A young mammal not yet weaned and still being fed milk by its mother. 

  • The act of suckling. 

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