currency vs paper money

currency

noun
  • Paper money. 

  • Money or other items used to facilitate transactions. 

  • The state of being current; general acceptance or recognition. 

paper money

noun
  • Cash in the form of banknotes. 

  • A type of joss paper resembling banknotes burnt to venerate the deceased, ancestor spirits, deities, etc. 

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