"a reminder of death," 1590s, a decorative object, usually an ornament for the person, containing emblems of death or reminders of the fleetingness of life, common in 16c., a Latin phrase, literally "remember to die," that is, "remember that you must die." From second person singular imperative of meminisse "to remember, recollect, think of, bear in mind" (a reduplicated form, related to mens "mind," from PIE root *men- (1) "to think") + mori "to die" (from PIE root *mer- "to rub away, harm" (also "to die" and forming words referring to death and to beings subject to death).
"amorous or designing widow," 1907, from the English title of Franz Lehar's operetta "Die Lustige Witwe" (1905). "The Lusty Widow" would have been more etymological (see lust (n.)), but would have given the wrong impression in English. Meaning "a type of wide-brimmed hat" (popularized in the play) is attested from 1908.
People are apt to sneeze, in hot weather for example; and people do not die of sneezing now-a-days, as they did in days that no one knows any thing about. We cannot give six draughts a-day, at one and nine pence each, for sneezing: call it the hay-fever. What a wonderful man! what a clever man! he understands the hay-fever: call him in! Thus is the hay-fever among the last in the list of fashionables. ["On Fashions in Physic," London Magazine, October 1825]