impairment vs pejoration

impairment

noun
  • A deterioration or weakening 

  • The result of being impaired 

  • A downward revaluation, a write-down. 

  • A disability or handicap 

  • an inefficient part or factor. 

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 impairment and pejoration occurred in a corpus of books? (source: Google Ngram Viewer )