merchant marine vs voyage

merchant marine

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

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

voyage

noun
  • A long journey, especially by ship. 

verb
  • To go on a long journey. 

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