mistress of ceremonies vs shop steward

mistress of ceremonies

noun
  • A woman who conducts a programme of varied entertainment, for example by introducing performers to the audience. 

shop steward

noun
  • A local member of a trade union elected to represent his fellow workers in discussions with the management at a workplace. 

How often have the words mistress of ceremonies and shop steward occurred in a corpus of books? (source: Google Ngram Viewer )