everglade vs pocosin

everglade

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

pocosin

noun
  • A low, wooded swamp in (especially coastal) Eastern Maryland or Virginia; a palustrine wetland with deep, acidic peat soils. 

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