chief petty officer vs warrant officer

chief petty officer

noun
  • A non-commissioned officer in the Royal Navy, ranking above petty officer and below warrant officer class 2. 

  • A warrant officer belonging to one of the two classes of chief petty officer: chief petty officer first class and chief petty officer second class. 

  • A non-commissioned officer in the United States Navy and United States Coast Guard, ranking above petty officer first class and below senior chief petty officer. 

warrant officer

noun
  • An officer holding rank by virtue of a warrant rather than a commission. 

  • An officer assigned to execute warrants and other writs. 

How often have the words chief petty officer and warrant officer occurred in a corpus of books? (source: Google Ngram Viewer )