To violate is to disobey a law or break an agreement, and an offender is a person who does so. A violator of the school dress code could wear a clown costume to school, and a copyright violator could copy his entire essay from a book. Violator comes from violare, «to treat with violence or shame» in Latin. Someone who breaks the rules is an offender. If your grandfather drives 90 miles per hour on the highway, he is breaking the speed limit.