apheresis vs blackout

apheresis

noun
  • Elision, suppression, or complete loss of a letter or sound (syllable) from the beginning of a word, such as the development of special from especial; procope. 

  • The removal of blood from a patient, and the removal of certain components (such as platelets) from that blood, followed by the transfusion of the filtered blood back to the donor (patient). 

blackout

noun
  • A temporary loss of consciousness. 

  • The blocking out of as much light as possible. 

  • A large-scale power failure, and resulting loss of electricity to consumers. 

  • A temporary loss of memory. 

  • The mandatory blocking of all light emanating from buildings, as well as outdoor and street lighting as a measure against aerial bombing or naval attack, as imposed during, e.g., World War II. 

  • An instance of censorship, especially a temporary one. 

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