spay vs sterilize

spay

verb
  • To remove or destroy the ovaries and/or uterus (of a female animal) so that she cannot become pregnant. 

noun
  • The act of spaying an animal. 

sterilize

verb
  • To deprive of the ability to procreate. 

  • To redact (a document), removing classified or sensitive material. 

  • To make unable to produce; to make unprofitable. 

  • To kill, deactivate (denature), or destroy (break apart) all living, viable microorganisms and spores on a surface, in a fluid, or contained in a compound, such as culture media or a medical product. 

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