plant room vs solarium

plant room

noun
  • A room used to house large machinery (plant), such as air-conditioning equipment. 

  • A room used to grow plants. 

solarium

noun
  • A room, rooftop, balcony, or terrace, used for its abundant sunlight (especially) when used as a medical treatment. 

  • Synonym of tanning salon, a room or business used for its sunlamps or tanning beds. 

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