Pareil VII was a planet, the seventh planet in orbit of the Pareil star system, located in or near Federation space in the galaxy's Alpha or Beta Quadrant.
History and specifics
At some point prior to 2265, James T. Kirk had seen Leonard McCoy save numerous lives on the planet using his medical skills. Kirk mentioned Pareil VII in an attempt to convince McCoy to sign on as chief medical officer aboard the USS Enterprise. (TOS - My Brother's Keeper novel: Enterprise)