Apocalypse vs Tribulation

Apocalypse

name
  • Revelation (last book of the Bible, composed of twenty-two chapters, which narrates the end of times) 

  • The written account of a revelation of hidden things given by God to a chosen prophet. 

Tribulation

name
  • (A period of) persecution before the Second Coming, lasting seven years, which Christians will experience worldwide which will purify and strengthen them. 

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