chicken feed vs medium of exchange

chicken feed

noun
  • A very small or insignificant quantity, especially of money. 

  • Food (usually grain) given to poultry. 

medium of exchange

noun
  • An intermediary used in trade to avoid the inconveniences of a pure barter system, such as money. 

How often have the words chicken feed and medium of exchange occurred in a corpus of books? (source: Google Ngram Viewer )