The Tetrahedron was an ancient, pre-Republic description of an area later known as the Arrowhead. It contained many of the founding worlds of the Galactic Republic, including Corellia, Coruscant, and Duro. It was named such because a Duros hyperspatial physicist believed that the planets of Alderaan, Coruscant, and Corellia, along with the Ginn Jump, were the four vertices of a perfect geometric pyramid.
In 1 BBY, Doctor Insmot Bowen, pre-Republic specialist at the Obroan Institute for Archaeology, mentioned the Humans of the Tetrahedron during a conversation with Bevel Lemelisk, Admiral Conan Antonio Motti and General Arhul Kurumenga, indicating that the term was still in use when related to historical events.