declination vs knockback

declination

noun
  • A refusal. 

  • At a given point, the angle between magnetic north and true north. 

  • At a given point, the angle between the line connecting this point with the geographical center of the earth and the equatorial plane. 

knockback

noun
  • A rejection; a refusal. 

  • A blow that causes the recipient to fall or move backwards, a knock back; a recoil. 

  • Something that impedes or reverses progress; a setback. 

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