Insidious is from in + Lat. sedere, sessus -to sit as well as president pre -before, dissident dis -apart, reside re -back, again, subside sub -under.
Lat. vadere, vasus -to walk appears in words invade, invasion, evade, evasion e, ex -out, pervasive, per -through.
And Palpatin could mean pale + psychopath from Gr. psyche -soul + pathos -suffering
You could look at Etymonline English etymological dictionary to see how etymology is created and also at Wiktionary.
And look at freelang and Whitakers words free latin dictionary, it can recognise many grammar forms and guess words, most etymology is based on latin.
Perhaps you as a writer will found inspiration in namemaking at my games etymologies page.