fen vs glade

fen

noun
  • A type of wetland fed by ground water and runoff, containing peat below the waterline, characteristically alkaline. 

  • A unit of currency in China, one-hundredth of a yuan. 

glade

noun
  • An open passage through a wood; a grassy open or cleared space in a forest. 

  • An everglade. 

  • An open space in the ice on a river or lake. 

  • A bright surface of ice or snow. 

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