lesson vs protreptic

lesson

noun
  • A severe lecture; reproof; rebuke; warning. 

  • A learning task assigned to a student; homework. 

  • A section of learning or teaching into which a wider learning content is divided. 

  • A section of the Bible or other religious text read as part of a divine service. 

  • Something learned or to be learned. 

  • An exercise; a composition serving an educational purpose; a study. 

  • Something that serves as a warning or encouragement. 

verb
  • To give a lesson to; to teach. 

protreptic

noun
  • A didactic speech, book, etc. 

adj
  • Serving to instruct; didactic. 

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