knit cap vs turban

knit cap

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

turban

noun
  • A man's headdress made by winding a length of cloth round the head. 

  • A woman's close-fitting hat with little or no brim. 

  • The complete set of whorls of a spiral shell. 

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