misfire vs spontaneous abortion

misfire

noun
  • An act of misfiring. 

verb
  • To fail to achieve the anticipated result. 

  • To fail to ignite in the proper sequence. 

  • To fail to discharge properly. 

spontaneous abortion

noun
  • A miscarriage. 

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