episode vs videocast

episode

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

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

videocast

noun
  • A vodcast. 

verb
  • To vodcast. 

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