Emissary

google

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early 17th century: from Latin emissarius ‘scout, spy’, from emittere ‘send out’ (see emit).

wiktionary

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From French émissaire, from Latin emissarius(“agent, scout, spy”).

etymonline

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emissary (n.)

"person sent on a mission," 1620s, from French émissaire (17c.) or directly from Latin emissarius "a scout, a spy," literally "that is sent out," from emissus, past participle of emittere "send forth" (see emit).