marsh hen vs moorhen

marsh hen

noun
  • Waterfowl of the familia Rallidae 

moorhen

noun
  • A female red grouse, Lagopus lagopus scotica. 

  • Any of various medium-sized water birds of the genus Gallinula, of the rail family, that feed in open water margins. 

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