Nana vs grandmammy

Nana

name
  • One's grandmother. 

  • A governess. 

  • A Japanese female given name from Japanese 

grandmammy

noun
  • Synonym of granddaddy (“something that is the greatest or most significant of its kind”) 

  • Grandmother. 

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