escalation vs lessening

escalation

noun
  • a deliberate or premeditated increase in the violence or geographic scope of a conflict 

  • The reassignment of a difficult customer problem to someone whose job is dedicated to handling such cases. 

  • an increase or rise, especially one to counteract a perceived discrepancy 

lessening

noun
  • A growing lesser; reduction or decrease. 

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