gunboat vs gunship

gunboat

noun
  • Any of the various types of small armed vessels. 

  • A couple of large shoes shoes. 

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 gunboat and gunship occurred in a corpus of books? (source: Google Ngram Viewer )