knockback vs repudiation

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. 

repudiation

noun
  • The act of refusing to accept; the act of repudiating. 

  • The young man's repudiation of the church's doctrines caused a conflict with his religious parents. 

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