depart vs lose the thread

depart

verb
  • To go away from; to leave. 

  • To leave. 

  • To die. 

  • To disappear, vanish; to cease to exist. 

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

  • To set out on a journey. 

lose the thread

verb
  • To get distracted and lose track of something (one's train of thought, a conversation). 

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