ketch vs sailing ship

ketch

noun
  • A fore-and-aft rigged sailing vessel with two masts, main and mizzen, the mizzen being stepped forward of the rudder post. 

  • A hangman. 

verb
  • To hang. 

sailing ship

noun
  • A ship with masts and sails, powered by the wind. 

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