alter vs confirm

alter

verb
  • To change the form or structure of. 

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

  • To tailor clothes to make them fit. 

  • To become different. 

  • 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. 

confirm

verb
  • To strengthen; to make firm or resolute. 

  • To administer the sacrament of confirmation on (someone). 

  • To assure the accuracy of previous statements. 

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