A QiVon was a symmetrical body part or organ in the Klingon anatomy.
The left QiVon of Dahar Master Kor would ache every time his ship hit warp eight. (DS9: "Blood Oath")
According to the script, QiVon was pronounced as "KEE-von". [1]
According to the Star Trek Encyclopedia, 3rd ed., p. 393, this was the Klingon word for "knee".