ladies' room vs the Ladies

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. 

the Ladies

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