depart vs go off at a tangent

depart

verb
  • To leave. 

  • To die. 

  • To disappear, vanish; to cease to exist. 

  • To go away from; to leave. 

  • To deviate (from), be different (from), fail to conform. 

  • To set out on a journey. 

go off at a tangent

How often have the words depart and go off at a tangent occurred in a corpus of books? (source: Google Ngram Viewer )