doughboy vs leatherneck

doughboy

noun
  • An American infantryman, especially one from World War I. 

  • A kind of flour dumpling. 

  • Frybread. 

leatherneck

noun
  • A soldier. 

  • Specifically, a marine. 

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