disturbance vs strengthening

disturbance

noun
  • The act of disturbing, being disturbed. 

  • A noisy commotion that causes a hubbub or interruption. 

  • Something that disturbs. 

  • An interruption of that which is normal or regular. 

  • A serious mental imbalance or illness. 

strengthening

noun
  • The process by which something is strengthened. 

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