ironclad vs man-of-war

ironclad

noun
  • An armor-plated warship, (especially) one preceding the invention of harveyized steel. 

  • A metal-plated ship, vessel, or vehicle. 

adj
  • Solid or certain; not able to be disputed or questioned; irrefutable. 

  • Covered with iron, steel, or some metal; armor-plated. 

  • Rigorous; severe; exacting. 

  • Stubborn; inflexible. 

man-of-war

noun
  • A powerful armed naval vessel, primarily one armed with cannon and propelled by sails; a warship. 

  • A man whose occupation is fighting in wars; a soldier, a warrior. 

  • The Arctic skua (Stercorarius parasiticus). 

How often have the words ironclad and man-of-war occurred in a corpus of books? (source: Google Ngram Viewer )