chador vs headscarf

chador

noun
  • A loose robe, made from a single cloth, worn as a combination head covering, veil and shawl by Muslim women, especially in Iran. 

headscarf

noun
  • A more or less square piece of material worn over the head, typically by women, often to protect the hair, or for religious reasons. 

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