pejoration vs worsening

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. 

worsening

noun
  • A worse situation; an aggravation or deterioration 

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