lifeline vs sustentation

lifeline

noun
  • System or structure of vital importance to a community. 

  • A particular crease in the palm. 

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

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

  • A means or route for transporting indispensable supplies. 

  • 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. 

sustentation

noun
  • The act or the result of sustaining; sustainment. 

  • The aggregate of the functions by which a living organism is maintained in a normal condition of weight and growth. 

  • The scheme by which the ministers of the Free Church of Scotland are supported by voluntary contributions not local or congregational, but with a national altruism or solidarity paid into a great central fund, out of which equal stipends are paid to all alike. 

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