In the past, the Originals were a world-renowned group. There were two meanings to this word—they were the ones who originally had the power, and later on, they taught their abilities to the whole world. The second were the ones who, during the Dalki war, decided to keep their powers to themselves and did not share them with the public.
The second definition of originals became more apparent later on as they grew with power. These secretive groups would become some of the strongest factions, families and travellers. And with how much time has passed, the world now thought they had access to every ability so far.
Even from the other Originals who had tried to keep their abilities secret. Perhaps the former didn't know how to teach or use the ability of the other Originals, but they knew of them. However, this all changed when the world came to know of the existence of the Chained.