billfold vs pocketbook

billfold

noun
  • A small, folding sleeve or case designed to hold paper currency, as well as credit cards, pictures, etc. 

pocketbook

noun
  • a purse or handbag. 

  • A small book, particularly (US) a paperback or (UK) notebook able to fit into a pocket. 

  • One's personal budget or economic capacity - the amount one can afford. 

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