attorney-in-fact vs interagent

attorney-in-fact

noun
  • An agent of the person giving him/her the power of attorney (for a specific purpose or for general purposes) to act on his or her behalf. The attorney-in-fact’s power and responsibilities depend on the specific powers granted in the power of attorney document. 

interagent

noun
  • An intermediate agent or middleman. 

How often have the words attorney-in-fact and interagent occurred in a corpus of books? (source: Google Ngram Viewer )