Carpi was an Alpha Quadrant planet claimed by the First Federation which was capable of sustaining Human life.
In 2266, Balok's pilot vessel attempted to tow the USS Enterprise to Carpi. He initially explained that once there, the crew would leave the Enterprise, which would be destroyed, and be interned. This effort was ultimately unsuccessful. (TOS: "The Corbomite Maneuver")
This planet's quadrant of origin is inferred based on the position of the government claiming it as seen in the star chart appearing in Star Trek VI: The Undiscovered Country.
This planet is not named on screen. The name "Carpi" is derived from the final draft script of "The Corbomite Maneuver" (dated 3 May 1966). The planet was unnamed but still referred to in the episode's second revised final draft script (dated 20 May 1966), which was the last full script draft submitted prior to the episode's production.