diminution vs pejoration

diminution

noun
  • A lessening, decrease or reduction. 

  • a compositional technique where the composer shortens the melody by shortening its note values. 

  • The act or process of making diminutive. 

pejoration

noun
  • The act or process of becoming worse; worsening or degeneration. 

  • The process by which a word acquires a more negative meaning over time. 

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