Word Origin & History
c.1400, "Psalm cxxxi in the Canon of the Mass" (which begins with the L. word Memento and in which the dead are commemorated), from L. memento "remember," imperative of meminisse "to remember," a reduplicated form, related to mens "mind." Meaning "reminder, warning" is from 1580s; sense of "keepsake"
is first recorded 1768.
"reminder of death," 1590s, from L., lit. "remember that you must die."