maternal aunt vs nanny

maternal aunt

noun
  • A similar great aunt, etc. 

  • A sister of one's mother. 

  • A sister-in-law of one's mother; the wife or ex-wife of a maternal uncle. 

nanny

noun
  • A grandmother. 

  • A child's nurse. 

  • A godmother. 

  • A female goat. 

verb
  • To treat like a nanny's charges; to coddle. 

  • To serve as a nanny. 

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