Spanish guitar vs classical guitar

Spanish guitar

noun
  • Synonym of classical guitar 

  • Synonym of Baroque guitar 

classical guitar

noun
  • A type of flat-tabled guitar of Spanish origin used primarily for Western classical music, flamenco, and Latin American music, with six nylon (formerly gut) strings, usually played with the fingers rather than with a plectrum. 

How often have the words Spanish guitar and classical guitar occurred in a corpus of books? (source: Google Ngram Viewer )