Palpatine’s body was the original. Being as dead looking and decayed as he was it reminded me of Darth Sion. Someone who died but with the strength of his hatred and use of the dark side willed his spirit to stay in his body, virtually allowing him immortality. Yes, palpatine was much more weak physically than sion, but the premise could be the same. I’m not sure about canon, but in legends palpatine’s master knew of Darth Malek and Revan, so he definitely should have know about sion the the other sith of that time.