Embassy
late 16th century (originally also as ambassy denoting the position of ambassador): from Old French ambasse, based on Latin ambactus ‘servant’. Compare with ambassador.
wiktionary
Modern variant of obsolete ambassy, from Middle French ambassee(“mission, embassy”), from Old French ambascee (also enbassee(“message for a high official, official mission”)) from Old Italian ambasciata, from Old Occitan ambaissada(“embassy”), derived from ambaissa(“message”), from Late Latin ambactia(“service rendered”) (attested also as ambascia, from Proto-Germanic *ambahtiją(“service”), *ambahtaz(“follower, servant”), from Gaulish ambaxtos(“dependant, vassal”, literally “one who is sent around”), from Proto-Celtic *ambaxtos(“servant”), from Proto-Indo-European* h₂m̥bʰi- h₂eǵ-(“drive around”); compare Latin ambactus, Old Irish amos, amsach(“mercenary, servant”), Welsh amaeth(“tenant farm”)). Doublet of ambassade.
etymonline
embassy (n.)
1570s, "position of an ambassador," from French embassee "mission, charge, office of ambassador," Old French ambassee, from Italian ambasciata, from Old Provençal ambaisada "office of ambassador," from Gaulish *ambactos "dependant, vassal," literally "one going around" (from PIE *amb(i)-ag-to, from roots *ambhi- "around" + *ag- "to drive, draw out or forth, move").
Meaning "official residence and retinue of an ambassador" is from 1764. In earlier use were embassade (late 15c.), ambassade (early 15c.), from Old French variant ambassade.
