https://en.wikipedia.org/wiki/Imperator

It is funny how, even after all those history classes, including a couple that dug a little deeper into Rome, we never covered this term. I knew that emperors used a pack of titles to give them the authority they claimed ... and even knew that this was one of them, but had never looked to find out directly what it meant to convey. (Answer: https://en.wikipedia.org/wiki/Imperium )