gist vs topic

gist

noun
  • The most essential part; the main idea or substance (of a longer or more complicated matter); the crux of a matter; the pith. 

verb
  • To summarize, to extract and present the most important parts of. 

topic

noun
  • Subject; theme; a category or general area of interest. 

  • Discussion thread. 

  • A musical sign intended to suggest a particular style or genre. 

adj
  • topical 

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