carr vs peat bog

carr

noun
  • A bog or marsh; marshy ground, swampland. 

  • rock 

  • A marsh or fen on which low trees or bushes grow; a marshy woodland. 

peat bog

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

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