Omeyocan

"The enemy of my enemy is my friend."

- Daniel Jackson translating what the alien giants said

The Giant Aliens are what the Tau'ri call the inhabitants of P7X-377. The species apparently exists in a different phase of visibility that Humans cannot naturally see. To compensate for this, they release massive amounts of neutrinos into the area, allowing humans to view them. In form, they appear as a mist like species. The Aliens are enemies of the Goa'uld, greeting each visitor to their planet with the words Oo ya waaling waaling wey tayil&mdash;the enemy of my enemy is my friend in Mayan. They visited Earth in the past, apparently before Ra conquered the planet, leaving a crystal skull behind to communicate with the Tau'ri. Nicholas Ballard, the grandfather of Daniel Jackson, discovered the skull and was transported to. Years later, Daniel himself visited the planet, but was temporarily out of phase due to Teal'c firiing a zat at the skull. After completing the process, the Aliens came, and repeated their mantra. Daniel realized that they were refering to the Goa'uld, and the Aliens allowed Nick to stay.

Behind the Scenes
The unpublished Fallout: Stargate Season Three sourcebook for the Stargate RPG developed by Alderac Entertainment named the giant aliens as the Tuohocan, though this was later overruled by the Stargate SG-1: City of the Gods novel, produced by Fandemonium, which named them the Omeyocan.