clock on vs shut down

clock on

verb
  • To record one's time of arrival at work, traditionally by inserting one's card into a timestamping machine. 

  • To begin work at the start of the day or start of one's shift. 

shut down

verb
  • To pass (another vehicle), especially quickly. 

  • To close, terminate, or end. 

  • To turn off or stop. 

  • To emotionally withdraw into oneself as a defense mechanism; to block out external stressors. 

How often have the words clock on and shut down occurred in a corpus of books? (source: Google Ngram Viewer )