mayoress vs syndic

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. 

syndic

noun
  • A government official having different duties depending on the country; also, a magistrate, especially one of the Chief Magistrates of Geneva, Switzerland. 

  • An agent of a corporation, or of any body of people engaged in a business enterprise; specifically, in the University of Cambridge, a member of the senate appointed to carry out specific duties. 

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