lyceum vs prep school

lyceum

noun
  • A school, especially European, at a stage between elementary school and college, a lycée. 

  • A public hall designed for lectures, readings, or concerts. 

  • An association for literary improvement. 

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 lyceum and prep school occurred in a corpus of books? (source: Google Ngram Viewer )