powder room vs restroom

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. 

restroom

noun
  • A room containing a public toilet: a public lavatory. 

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