armada vs merchant marine

armada

noun
  • Any large army or fleet of military vessels. 

  • A large flock of anything. 

  • A fleet of warships, especially with reference to the Spanish Armada. 

merchant marine

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

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

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