disclaimer vs knockback

disclaimer

noun
  • A denial, disavowal, or renunciation, as of a title, claim, interest, estate, or trust; relinquishment or waiver of an interest or estate. 

  • A public disavowal, as of responsibility, pretensions, claims, opinions, etc. 

  • One who disclaims, disowns, or renounces. 

  • A disclosure of an interest, relationship, or the like. 

verb
  • To disclaim or disavow, as by appending a legal disclaimer. 

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 disclaimer and knockback occurred in a corpus of books? (source: Google Ngram Viewer )