departyoudaoicibaDictYouDict[depart 词源字典]
depart: [13] Depart originally meant ‘divide’. This was the sense of its ultimate Latin ancestor dispertīre, literally ‘separate up into constituent parts’, a compound verb formed from the prefix dis-, denoting separation, and partīre ‘divide, distribute’, a derivative of the noun pars ‘part’. It passed into English via Vulgar Latin *dēpartīre and Old French departir, by which time the notions of ‘division’ and ‘separation’ had already produced the intransitive sense ‘go away’.
=> part[depart etymology, depart origin, 英语词源]
depart (v.)youdaoicibaDictYouDict
mid-13c., "part from each other," from Old French departir (10c.) "to divide, distribute; separate (oneself), depart; die," from Late Latin departire "divide" (transitive), from de- "from" (see de-) + partire "to part, divide," from pars (genitive partis) "a part" (see part (n.)).

As a euphemism for "to die" (to depart this life; compare Old French departir de cest siecle) it is attested from c. 1500, as is the departed for "the dead," singly or collectively. Transitive lingers in some English usages; the wedding service was till death us depart until 1662. Related: Departed; departing.