Etymology tree Proto-Indo-European *h₂éd Proto-Italic *ad Proto-Italic *ad- Latin ad- Proto-Indo-European *gʰredʰ-der. Latin gradior Latin aggredior Proto-Indo-European *-tōr Proto-Italic *-tōr Latin -tor Latin aggressorder. English aggressor Derived from Latin aggressor (“attacker, assailant, aggressor”).