brigantine vs gaff-rigged sailboat

brigantine

noun
  • a two-masted vessel, square-rigged on the foremast, but fore-and-aft-rigged mainsail with a square-rig above it on the mainmast. 

gaff-rigged sailboat

How often have the words brigantine and gaff-rigged sailboat occurred in a corpus of books? (source: Google Ngram Viewer )