aviator vs ramjet

aviator

noun
  • An aircraft pilot. The use of the word may imply claims of superior airmanship, as in navy aviator vs. air force pilot. 

ramjet

noun
  • A jet engine in which forward motion forces air into an inlet, compressing it (as opposed to having a pump type device compressing the air for combustion with fuel), and where combustion is subsonic. 

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