Fag.

One who does, and perseveres in doing. In public schools, it means a little boy who waits upon a bigger one. Probably a contracted form of factor, factotum; Latin, fac-ĕre, to do.

Fag. Servant of Captain Absolute, who apes his master in all things. (Sheridan: The Rivals.)

“Even the mendacious Mr. Fag assures us, though he never scruples to tell a lie at his master’s command, yet it hurts his conscience to be found out.”—Sir Walter Scott.