embassy: [16] Ultimately, embassy comes from the same source as ambassador, the Vulgar Latin verb *ambactiāre ‘go on a mission’ (a derivative, via a rather circuitous route, of Latin ambactus ‘vassal’, which was of Celtic origin). From the verb was derived the Old French noun ambassade, which was borrowed into English in the 15th century but was gradually supplanted from the 16th century onwards by embassy, acquired from another Old French derivative ambassee. => ambassador[embassy etymology, embassy origin, 英语词源]