beret vs knit cap

beret

noun
  • A type of round, brimless cap with a soft top and a headband to secure it to the head; usually culturally associated with France. 

knit cap

noun
  • A soft, head-hugging cap usually without a specified front or back, barring those with designs or logos 

How often have the words beret and knit cap occurred in a corpus of books? (source: Google Ngram Viewer )