An emissary is often a person who is sent somewhere in order to act as a representative. The key in that sentence is sent; emissary derives from Latin emissus, the past participle of the verb emittere, meaning “to send out.”  By the early 17th century, it was commonly seen and heard word. An earlier common emittere descendant is emit. In addition, emittere itself comes from Latin mittere (“to send”), which is an ancestor of many English words, including admit, commit, mission, omit, permit, premise, promise, and submit.

Examples

“America has a long tradition of deploying political emissaries. They can have the authority of a direct line to the president.” — The Economist, 13 Aug. 2020

“He had founded that fellowship of the Black Arrow, as a ruined man longing for vengeance and money; and yet among those who knew him best, he was thought to be the agent and emissary of the great King-maker of England, Richard, Earl of Warwick.” — Robert Louis Stevenson, The Black Arrow, 1888