covert vs frith

covert

noun
  • Area of thick undergrowth where animals hide. 

  • A covering. 

  • A disguise. 

  • A feather that covers the bases of flight feathers. 

  • A hiding place. 

adj
  • Under coverture. 

  • Secret, surreptitious, concealed. 

frith

noun
  • Brushwood or undergrowth, sometimes in the form of a hedge. 

  • A forest or wood; woodland generally. 

  • Land with mostly undergrowth and few trees; also, land in between forests or woods; pastureland which is not in use. 

  • A hedge, especially one made from brushwood which has been wattled; also, a movable frame made from wattled branches, a hurdle. 

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