sauna vs spa

sauna

noun
  • A public sauna. 

  • A very hot place or room. 

  • A room or a house designed for heat sessions. 

  • The act of using a sauna. 

  • In some countries, a business with bath-like facilities that is actually a brothel or a place for (non-commercial) sexual encounters; a bathhouse. 

verb
  • To use a sauna. 

spa

noun
  • A health resort near a mineral spring or hot spring. 

  • A trendy or fashionable resort. 

  • A convenience store. 

  • A health club. 

  • A hot tub. 

  • A clumsy person (see spastic) 

  • An idiot; a gobshite 

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