directrix vs film director

directrix

noun
  • A female who directs; a directress. 

  • A line used to define a curve or surface; especially a line, the distance from which a point on a conic has a constant ratio to that from the focus. 

film director

noun
  • A person who directs and supervises the production of a movie, especially as profession. 

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