institute vs prep school

institute

noun
  • An institution of learning; a college, especially for technical subjects 

  • An organization founded to promote a cause 

  • The person to whom an estate is first given by destination or limitation. 

  • The building housing such an institution 

verb
  • To invest with the spiritual charge of a benefice, or the care of souls. 

  • To nominate; to appoint. 

  • To begin or initiate (something); to found. 

prep school

noun
  • A private or public school intended to prepare its students to get into prestigious universities. 

  • A private primary school which prepares its pupils for the common entrance examination most commonly at the age of thirteen, and subsequent entry into public school. 

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