Cave vs Thunder

Cave

name
  • The 18th sura (chapter) of the Qur'an. 

  • A village in Lincoln County, Missouri, United States. 

  • A town and comune in Lazio, Italy. 

  • A settlement in Timaru district, Canterbury, New Zealand. 

  • An unincorporated community in Pendleton County, West Virginia, United States. 

  • A surname. 

Thunder

name
  • The 13th sura (chapter) of the Qur'an. 

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