mayoress vs mer

mayoress

noun
  • A daughter or female friend of a male mayor chosen by him to hold the title mayoress. 

  • The wife of a (male) mayor. 

  • A female mayor. 

mer

noun
  • merpeople 

  • A repeat unit: a structural unit which through repetition forms a polymer. 

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