I wouldn't be so sure. "Imperātor" is a Latin word meaning "leader" or "commander." "Rex" is the word for "king" which was what the kings of Rome (that is, the emperors) were too ashamed to call themselves. Instead they projected power through endless propaganda while they claimed simply to be "first among the equals" (Princeps).
Just to poke a few no-history-required holes in your surety!