from
The Collaborative International Dictionary of English v.0.48
Imperator \Im`pe*ra"tor\, n. [L. See {Emperor}.] (Rom. Antiq.)
A commander; a leader; an emperor; -- originally an
appellation of honor by which Roman soldiers saluted their
general after an important victory. Subsequently the title
was conferred as a recognition of great military achievements
by the senate, whence it carried with it some special
privileges. After the downfall of the Republic it was assumed
by Augustus and his successors, and came to have the meaning
now attached to the word emperor.
[1913 Webster]