plumage vs rectrix

plumage

noun
  • Layer or collection of feathers covering a bird’s body; feathers used ornamentally; feathering. 

  • Finery or elaborate dress. 

rectrix

noun
  • A flight feather on the tails of birds, used for directional control. 

  • A governess; a rectoress. 

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