cohere vs unfasten

cohere

verb
  • To stick together physically, by adhesion. 

  • To be consistent as part of a group, or by common purpose. 

unfasten

verb
  • To come unloosed or untied. 

  • To detach from any connecting agency or link; to disconnect. 

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