advocacy vs countersignature

advocacy

noun
  • the practice of supporting someone to make their voice heard 

  • the profession of an advocate 

  • the act of arguing in favour of, or supporting someone or something 

countersignature

noun
  • A signature made to confirm or endorse another. 

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