episode vs occurrence

episode

noun
  • An incident, action, or time period standing out by itself, but more or less connected with a complete series of events. 

  • An instalment of a drama told in parts, as in a TV series. 

occurrence

noun
  • An actual instance when a situation occurs; an event or happening. 

  • The lexical aspect (aktionsart) of verbs or predicates that change in or over time. 

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