caliph vs shah

caliph

noun
  • The political leader of the Muslim world; the successor of the prophet Muhammad's political authority. 

shah

noun
  • A supreme ruler in some Middle Eastern or South Asian nations. 

  • A king of Persia or Iran. 

  • A Ukrainian monetary unit. 

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