covert vs rectrix

covert

noun
  • A feather that covers the bases of flight feathers. 

  • A covering. 

  • A disguise. 

  • Area of thick undergrowth where animals hide. 

  • A hiding place. 

adj
  • Under coverture. 

  • Secret, surreptitious, concealed. 

rectrix

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

  • A governess; a rectoress. 

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