offing vs rubout

offing

noun
  • The area of the sea in which a ship can be seen in the distance from land, excluding the parts nearest the shore, and beyond the anchoring ground. 

  • The distance that a ship at sea keeps away from land, often because of navigational dangers, fog and other hazards; a position at a distance from shore. 

  • The foreseeable future. Chiefly in the phrase in the offing. 

rubout

noun
  • An assassination. 

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