men's room vs women's room

men's room

noun
  • A lavatory intended for use by men, often including urinals in addition to toilets. 

  • Other rooms intended for use by men, as waiting rooms, dressing rooms, locker rooms, etc. 

women's room

noun
  • Synonym of ladies' room: a public lavatory intended for women. 

  • A waiting room in a railway station or other public building intended exclusively for women and usually including a separate women's lavatory. 

How often have the words men's room and women's room occurred in a corpus of books? (source: Google Ngram Viewer )