cargo vs merchant marine

cargo

noun
  • Freight carried by a ship, aircraft, or motor vehicle. 

  • Western material goods. 

merchant marine

noun
  • A ship dedicated to commercial, rather than military, purposes. 

  • Synonym of merchant navy. The fleet considered as an entire combined force. 

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