“Outrage” derives from the Latin word ultraticum, which meant “excessive.” The root is ultra, which in Latin means “beyond” or “extremely,” just like it does in English.   Outrageous came to English from the Old French outrage (excessive) to the Old French Outrageus  to outrage and outrageous in late Middle English. 

The earliest known use of the word outrageous is in the Middle English period (1150—1500). OED's earliest evidence for outrageous is from before 1325, in Statutes of the Realm.

This is a very important word. I use it all the time, even using synonyms, but it isn't enough.