singer-songwriter vs troubadour

singer-songwriter

noun
  • A musician who both sings and composes, especially when recording or performing his/her own compositions. 

troubadour

noun
  • An itinerant composer and performer of songs in medieval Europe; a jongleur or travelling minstrel. 

How often have the words singer-songwriter and troubadour occurred in a corpus of books? (source: Google Ngram Viewer )