separate off vs turn off

separate off

turn off

verb
  • To repulse, disgust, or discourage (someone). 

  • To leave a road; to exit. 

  • To become deactivated; to become powered down. 

  • To power down, to switch off, to put out of operation, to deactivate (an appliance, light, mechanism, functionality etc.). 

  • To rotate a tap or valve so as to interrupt the outflow of liquid or gas. 

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