alter vs variate

alter

verb
  • To become different. 

  • To castrate, neuter or spay (a dog or other animal). 

  • To change the form or structure of. 

  • To tailor clothes to make them fit. 

  • To affect mentally, as by psychotropic drugs or illness. 

noun
  • An identity or headmate of a person with dissociative identity disorder (previously known as multiple personality disorder). A member of a system. 

variate

verb
  • To alter; to vary; to make or become different. 

noun
  • The measured magnitude of a variable. 

  • random variable 

  • A variable, often the set of x values plotted on a graph. 

  • A measurable quantity capable of taking on a number of values. 

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