baroness vs caliph

baroness

noun
  • A woman holding a baronial title in her own right; a female ruler of a barony. 

  • The wife of a baron. 

caliph

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

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