everglade vs muskeg

everglade

noun
  • A tract of marshland, especially one containing clumps of sawgrass and hammocks of vegetation 

muskeg

noun
  • A terrain composed of peat bog with tussocky meadow and woody vegetation including spruce. 

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