flechette vs revolver

flechette

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

revolver

noun
  • A handgun with a revolving chamber enabling several shots to be fired without reloading. 

  • Any (personal) firearm with such a mechanism. 

  • Synonym of revolving line of credit 

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