Short answers, pulled from the story.
The name Palpatine did not appear until Alan Dean Foster wrote the novelization of Star Wars in 1976. The surname Palpatine emerged from that text, while the first name Sheev arrived much later in the 2014 novel Tarkin.
Ian McDiarmid took over the role physically and provided the voice for the character after Clive Revill voiced him in The Empire Strikes Back. Lucas and director Richard Marquand reversed course to keep McDiarmid's distinctive voice instead of dubbing it.
George Lucas explicitly cited Napoleon Bonaparte, Alberto Fujimori, Ferdinand Marcos Sr., and Adolf Hitler as influences on the character. He also drew inspiration from Richard Nixon when considering how democracies turn into dictatorships.
Palpatine manipulated events on Naboo while posing as Senator Sheev Palpatine by engineering the Trade Federation invasion. He deceived Queen Padmé Amidala into calling for a motion of no confidence against Supreme Chancellor Finis Valorum before getting elected as Chancellor of the Republic.
Rey used the power of past Jedi to face Palpatine once more and deflected his lightning using Skywalker lightsabers. This action killed Palpatine and destroyed his Sith forces while revealing his rotting hands and pupil-less true form.