call back vs nullify

call back

noun
  • Request for a second interview or audition, following a successful initial interview. 

verb
  • To request someone's return. 

  • To telephone someone again at a more convenient time. 

  • To return to a shop or residence one has previously visited. 

nullify

verb
  • To prevent from happening. 

  • To make of no use or value; to cancel out. 

  • To make legally invalid. 

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