The Klingon home planet wasn't formally named until Star Trek VI: The Undiscovered Country, and it would still be years before the name stuck. The Klingons debuted all the way back in the Star Trek: The Original Series season 1 episode "Errand Of Mercy." They would go on to be Captain Kirk's most frequent adversary, maintaining a constant presence on TOS and in the proceeding TOS movies.
The Star Trek: The Original Series era Klingons were always portrayed as militaristic conquerors who were ideologically opposed to the idyllic, peaceful Federation. Even though the Klingons and Federation would go on to form an alliance by the era of Star Trek: The Next Generation, the fierce warrior race was still considered one of the major powers in the Alpha Quadrant. TNG would finally show the Klingon's home planet onscreen in the season 3 episode "Sins Of The Father." One problem remained, however – the planet still didn't have a name.
