^Oh, come on. "Sidious" is obviously short for "insidious," just as "Vader" can be taken as short for "invader" (although Lucas has claimed he coined "Darth Vader" as a blend of "dark father" and "deathwater"). Futurama even did a joke about this
once. Really, with names like "Maul" and "Tyrannus" and "Plagueis," Sith name etymologies are quite easy to figure out. You're overthinking it.
The name "Palpatine" is probably a variant on the Palatine Hill in Rome, traditionally seen as the origin of Rome and its empire, and the site where many Roman emperors lived. Its name is derived from the word for "palace." So here's a case where an obvious Latin derivation for the name does present itself, and somehow you still missed it. (The name Palpatine first appeared in the original Star Wars
novelization in 1977, years before the character appeared onscreen and was given a pale face.)
And Jedi is a Hebrew name meaning "beloved/protected by God," although it's more likely
that Lucas just based the word on "jed" and "jeddak" from Edgar Rice Burroughs's Barsoom novels, one of his major inspirations for Star Wars