Source : Webster's Revised Unabridged Dictionary (1913)

Memento \Me*men"to\, n.; pl. {Mementos}. [L., remember, be
   mindful, imper. of meminisse to remember. See {Mention}.]
   A hint, suggestion, token, or memorial, to awaken memory;
   that which reminds or recalls to memory; a souvenir.

         Seasonable mementos may be useful.       --Bacon.