demise (n.)

mid-15c., "transference of property, grant of land for life or a period of years," via Anglo-French from Old French demis, fem. past participle of desmetre "dismiss, put away" (Modern French démettre), from des- "away" (from Latin dis-) + metre "put," from Latin mittere "let go, send" (see mission).

Originally especially "a conveyance of an estate by will or lease," then "transfer of sovereignty," as by the death or deposing of a king (1540s). The sense was transferred to "death" (as the occasion of such a transfer) by 1754, at first especially the death of a sovereign or other important person, but also as a euphemism for "death."