inaugurate vs usher in

inaugurate

verb
  • To dedicate ceremoniously; to initiate something in a formal manner. 

  • To induct into office with a formal ceremony. 

adj
  • Invested with office; inaugurated. 

usher in

verb
  • To begin something with preparatory material; to introduce. 

  • To announce the arrival of something; to herald. 

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