capital ship vs gunship

capital ship

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

gunship

noun
  • A ship equipped with heavy artillery. 

  • An armed helicopter tasked to attack the enemy. 

  • A transport airplane equipped with large calibre guns typical of armoured fighting vehicles 

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