comfort station vs ladies' room

comfort station

noun
  • A public lavatory. 

ladies' room

noun
  • A public lavatory intended for use by women. 

  • 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. 

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