L-374 II
From Memory Alpha, the free Star Trek reference
L-374 II is a planet in the L-374 system, which lost two planets in the planet killer attack of 2267.
When the crew of the badly-damaged USS Constellation was unaccounted for after the planet killer's attack, Spock considered it improbable that the ship's crew had fled to L-374 II as this planet has an atmosphere poisonous to Humans. (TOS: "The Doomsday Machine")
