anticlimax vs swan song

anticlimax

noun
  • An unsatisfying resolution to a narrative, usually owing to a deus ex machina or similarly trivial resolution of the main conflict. 

  • An abrupt descent (either deliberate or unintentional) from the dignity of the idea which the speaker or writer appeared to be aiming for. 

swan song

noun
  • A final performance or accomplishment, especially one before retirement. 

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