mammy vs old lady

mammy

noun
  • mamma; mother 

  • In the southern United States, a black nanny employed to look after white children; or in the antebellum South, a female slave who was close to the household and looked after the children. 

old lady

noun
  • One's mother. 

  • The Bank of England, sometimes referred to as the “Old Lady of Threadneedle Street” or simply “The Old Lady”. 

  • A queen. 

  • An elderly woman. 

  • One's girlfriend, wife or significant other. 

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