capital ship vs ironclad

capital ship

noun
  • Any of the most important types of warships, capable of projecting a fleet in being. 

ironclad

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

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

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. 

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