freighter vs merchantman

freighter

noun
  • A vessel used mainly to carry freight; a cargo ship. 

  • One employed in receiving and forwarding freight. 

  • An aircraft used mainly to carry freight; a cargo aircraft or cargo plane. 

  • One for whom freight is transported. 

  • One who loads a ship, or one who charters and loads a ship. 

merchantman

noun
  • A cargo ship, engaged in commercial activities, as opposed to a warship. 

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