ladies' room vs small room

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. 

small room

noun
  • A lavatory: a room intended for urination and defecation. 

  • Used other than figuratively or idiomatically: see small, room. 

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