666 was historically used by the jews to say Nerō Kaisar assigning his rule the mark of the beast.The Latin version of the name drops the second Nun (נ), so that it appears as Nro and transliterates into Hebrew as נרו קסר, yielding 616.
It was only after the frankist jews rediscovering their religion and further the illuminati assigning 666 to satanism and selling fake satanism to their illuminatus members to create mass disinformation ,to hide the jewish element behind this and to shift blame to a clown satanism patsy that they created themselves.
666 is eastern occult gematria is the kaballistic square of the sun.