ladies' room vs operating theatre

ladies' room

noun
  • A room belonging to or intended for some or all women 

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

  • A public lavatory intended for use by women. 

operating theatre

noun
  • A room in a hospital used for performing surgery (originally designed for operations in front of observers). 

How often have the words ladies' room and operating theatre occurred in a corpus of books? (source: Google Ngram Viewer )