Geonosis only ever appeared on screen in one Star Wars movie, but it was essential in the construction of the Death Star and had a secret cameo in Star Wars: Episode III - Revenge of the Sith. The wide canon of Star Wars lore includes a myriad of planets, and the films themselves feature worlds that range from Tattooine, which appears in more installments than any other planet, to those that are never even officially named. Revenge of the Sith specifically featured a number of never-before-seen planets, many of which were introduced in the Order 66 montage.
Geonosis first appeared in Star Wars: Episode II - Attack of the Clones as the secret base of the site of a sizeable factory being used to construct battle droids. The planet served as the first capital of the Confederacy of Independent Systems in the time leading up to the film, and would also go on to host the first skirmish of the Clone Wars when the Battle of Geonosis broke out. These events tie it integrally to the plotlines of the prequel trilogy, but are also key to setting up part of the original trilogy.
Although the Death Star was mobile, much of its initial construction occurred over Geonosis. This means that during the shot near the end of Revenge of the Sith in which the newly-christened Darth Vader and Emperor Palpatine observe the construction of the battle station, their Star Destroyer is in fact orbiting the (unseen) desert world. The film doesn't draw particular attention to the location, as this was hardly the focus of the scene, but general knowledge of this small fact has only become less likely with the release of Rogue One: A Star Wars Story, which shows work being done on the Death Star while it is in orbit over its second home, Scarif.
The name "Geonosis" was most likely inspired by the uncommon word "geognosis," which means knowledge of the earth, probably simply in relation to its visual identity as a very rocky, earthy planet. However, the Geonosians were the original architects of the Death Star, a small hologram of which can even be seen in Attack of the Clones, suggesting another possible referent: Geonosis is the literal source of knowledge about this constructed world.
In keeping with the traditions of sci-fi adventure stories, Star Wars features many fantastical planets that provide compelling backdrops to its set pieces. However, there's a certain hierarchy defined by which are most recognizable in pop culture, and while Geonosis has an entire history all its own, an appearance by the Death Star will necessarily overshadow it. Thankfully, the library of Star Wars stories is vast and varied, and The Clone Wars series was able to show Geonosis in more detail.