instigator

From Latin īnstīgātor (“stimulator”), from īnstīgāre (present infinitive of īnstīgō (“to incite, set on, stimulate, rouse or urge”), possibly from Proto-Indo-European (s)teyg- (“to be sharp, to stab; to puncture; to goad”)) + -or (from -ō (suffix forming masculine agent nouns), from Proto-Indo-European -h₃onh₂- (suffix forming nouns denoting authority or burden)); cognate with French instigateur. By surface analysis, instigate + -or.