decampment vs emigration

decampment

noun
  • A prompt departure. 

  • The act of decamping. 

emigration

noun
  • The act of emigrating; movement of a person or persons out of a country or national region, for the purpose of permanent relocation of residence. 

  • A body of emigrants; emigrants collectively. 

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