fire up vs key up

fire up

verb
  • To excite; to infuse with energy. 

  • Of an engine or similar, to start. 

  • To ignite. 

  • To launch; to run. 

key up

verb
  • To raise the intensity, excitement, tension, etc., of. 

  • To produce nervous tension in. 

  • To raise the pitch of. 

  • To raise (the whole ring of an arch) off its centering, by driving in the keystone forcibly. 

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