doughboy vs serviceman

doughboy

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

  • A kind of flour dumpling. 

  • Frybread. 

serviceman

noun
  • A man who serves in the armed forces. 

  • A person, especially a man, employed in service and maintenance of equipment. 

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