Earth Mother vs Terra

Earth Mother

noun
  • The Great Goddess of the Earth and fertility. 

  • A figurine or depiction of this goddess. 

Terra

name
  • The planet Earth. 

  • A female given name. 

  • The Roman earth goddess, equivalent in the interpretatio graeca to Gaea. 

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