flechette vs missile

flechette

noun
  • A small sharp antipersonnel projectile, used as shrapnel, fired from a shotgun, or scattered from an aircraft. 

missile

noun
  • Any object used as a weapon by being thrown or fired through the air, such as stone, arrow or bullet. 

  • A self-propelled projectile whose trajectory can be adjusted after it is launched. 

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