downtime vs shutdown

downtime

noun
  • The amount of time lost due to forces beyond one's control, as with a computer crash. 

  • A period of time set aside for rest and relaxation; leisure time. 

shutdown

noun
  • The action of stopping operations; a closing, of a computer, business, event, etc. 

  • A statement, insult, etc. that prevents the opponent from replying further. 

  • An autistic response to stress or sensory overload, in which the individual freezes up and becomes silent, motionless, and unresponsive. 

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