placate vs steam up

placate

verb
  • To calm; to bring peace to; to influence someone who was furious to the point that they become content or at least no longer irate. 

steam up

verb
  • To become steamy. 

  • To become coated with condensation. To fog up. 

  • To bring (a steam boiler) up to working steam pressure. 

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