Tei Tenga

Tei Tenga is a fictional moon or planet where Doom was originally supposed to take place during its first and third episodes, according to Tom Hall's preliminary design document for the game.

The celestial body always faces the same way towards the star it orbits, and thus doesn't have day and night cycles. Because of this, it is divided into two sections, a continually bright face called the Lightside, and a complementary sunless face called the Darkside.

Although it is initially referred to as the giant moon Tei Tenga, it is called a planet in a few other instances.

Tei Tenga does appear in the finished Doom games, although somewhat obscurely, being named in some of the computer console display textures. Additionally, some fan-made PWADs expand on the Tei Tenga concept.

The meaning may come from Chinese. In Spanish "Te tengo" means "I've got you".