escalation vs tailing off

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 

tailing off

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