alteration vs refitting

alteration

noun
  • The act of altering or making different. 

  • The state of being altered; a change made in the form or nature of a thing; a changed condition. 

refitting

noun
  • The act by which something is refitted; a refit. 

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