everglade vs polder

everglade

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

polder

noun
  • An area of ground reclaimed from a sea or lake by means of dikes. 

verb
  • To reclaim an area of ground from a sea or lake by means of dikes. 

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