In 'The Nickpickers Guide for Next Generation Trekkers Vol II' (I think), Phil Farrand notes that there was a planet which was on the Federation side of a border with a hostile alien species in TOS. After a cease fire and neutral zone was established, the planet was on the wrong side of the border so the colonists were ordered to move, which they did unhappily.

A generation later in TNG, a planet with the exact same name was on the wrong side of a different border (probably somewhere in the Cardassian Neutral Zone this time?) Rather than the most likely explanation that the script writers were lazy and made a mistake, Farrand notes that its more fun to imagine the colonists re-settled a new planet and named it after the old, only to have the Federation come in and yet again forcibly relocate them, giving good justification for their dissatisfaction and anger.

What planet was this?