downfall vs lifeline

downfall

noun
  • An act of falling down. 

  • The cause of such a fall; a critical blow or error. 

  • A precipitous decline in fortune; death or rapid deterioration, as in status or wealth. 

verb
  • To fall down; deteriorate; decline. 

lifeline

noun
  • A line to which a drowning or falling victim may cling. 

  • A particular crease in the palm. 

  • A line from the diver to a tender at the surface control point. 

  • A means or route for transporting indispensable supplies. 

  • System or structure of vital importance to a community. 

  • A source of salvation in a crisis. 

  • On the deck of a boat, a line to which one can attach oneself to stay aboard on rough seas. 

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