Sei (清) in Sei Shonagon indicated she was from the Kiyohara (清原) clan, and Murasaki (紫) in Murasaki Shikibu came from Murasaki no ue (紫の上), a character of her novel "Tale of Genji," according to one view.
清少納言の「清」は清原氏の出自であることを示し、紫式部の「紫」は彼女の著作源氏物語の紫の上にちなむ（他説あり）。