certify vs repel

certify

verb
  • To attest to (a fact) as the truth. 

  • To attest that a product, service, organization, or person has met an official standard. 

  • To authenticate or verify in writing. 

repel

verb
  • To cause repulsion or dislike in; to disgust. 

  • To ward off (a malignant influence, attack etc.). 

  • To drive back (an assailant, advancing force etc.). 

  • To reject, put off (a request, demand etc.). 

  • To save (a shot). 

  • To force away by means of a repulsive force. 

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