[throwaway2048]

Imperator (in English Emperor) was a title specifically invented by Augustus to avoid the title king. It might be roughly translated as "Commander", in a military sense.

[scott_w]

That's definitely not correct. The first sentences in Wikipedia date its use to the Roman Kingdom and Republic, long before Augustus: https://en.wikipedia.org/wiki/Imperator

[JumpCrisscross]

Soldiers hailing their commanders Imperator on the battlefield was a requirement for a triumph under the Republic. Octavian did not invent the title.

[boomboomsubban]

You're right, he did go by imperator, my memory is poor, but his primary titles provided by the senate were "augustus" and "princeps."