Midgard vs Mother Earth

Midgard

name
  • The Earth of traditional Germanic cosmology, conceived as a middle realm between heaven (Asgard) and hell (Helheim); the abode of human beings, between those of the gods (Æsir) and the dead. 

Mother Earth

name
  • The goddess of the earth in various cultures. 

  • The personification of the Earth, (chiefly) conceived as a fertile, nurturing, and loving mother. 

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