merchant marine vs steerage

merchant marine

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

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

steerage

noun
  • The effect of the helm on a ship. 

  • The section of a passenger ship that provided inexpensive accommodation with no individual cabins. 

  • The art of steering. 

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