Jaffs were the descendants of the Jaffa who rebelled against their false god Marduk on the planet Zigara. Though the original priests and warriors who rebelled against Marduk died when their symbiotes matured, whom they took with them to the grave, in the time since their rebellion they had taken wives and had children who matured to be genetically different from their parents; they did not need a symbiote to survive. It was through these people that the history of the planet Zigara was kept alive through oral traditions; they remembered Marduk for being a false god rather than simply a legend as the Zigarans did.
When the Stargate was uncovered thousands of years after it had been buried by the original rebellion, it was the Jaffs who petitioned the government to rebury it. Though the government didn't follow this advice, they did agree to increase the funding into reverse-engineering the technology found near the Stargate; this resulted in the X-750 Force Rifle among other inventions which were all that kept the people of Zigara from falling to Bel's forces when they attacked. (RPG: "Living Gods: Stargate System Lords")