peat bog vs polder

peat bog

noun

  • a bog in which the soil is formed from peat. 

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 peat bog and polder occurred in a corpus of books? (source: Google Ngram Viewer )