du'a' vs supplication

du'a'

noun
  • private prayer by an individual 

supplication

noun
  • A prayer or entreaty to a god. 

  • The process by which a doctorate at Oxford university is officially requested after a thesis has been approved. 

  • In Ancient Rome, a solemn service or day decreed for giving formal thanks to the gods for victory, etc. 

  • An act of supplicating; a humble request. 

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