mum vs quiet as a mouse

mum

adj
  • Silent. 

  • Secret. 

verb
  • To act in a pantomime or dumb show. 

noun
  • Mother. 

  • A type of strong beer, originally made in Brunswick, Germany. 

  • A decoration made originally of a real chrysanthemum but now usually an artificial (silk) flower combined with ribbons and marked with such indicators as the wearer's name, school name, the year, and so on; traditionally worn by girls at high school homecoming celebrations. 

  • A chrysanthemum. 

intj
  • stop speaking!, stop talking!, hush! 

quiet as a mouse

adj
  • Very quiet, so as to not be heard 

How often have the words mum and quiet as a mouse occurred in a corpus of books? (source: Google Ngram Viewer )