powder room vs women's room

powder room

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

  • A room used to powder hair and wigs. 

  • A room used to store gunpowder, particularly (historical) on a ship equipped with cannon. 

  • Synonym of half bath: a small room with a toilet and sink but no bathtub or shower. 

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 powder room and women's room occurred in a corpus of books? (source: Google Ngram Viewer )