late 14c., "fame, renown, reputation," also "a commemorative gesture, monument, or rite;" in general, "something by which the memory of a person, thing, or event is preserved," from Old French memorial "record, report," and directly from Late Latin memoriale "a memorial," noun use of neuter of Latin memorialis (adj.) "of or belonging to memory," from memoria "memory" (from PIE root *(s)mer- (1) "to remember").
Meaning "memorial act, commemorative gesture, monument, etc.," is from late 14c., as is the sense of "a written representation of facts made to a legislative or other body as the grounds for a petition." Related: Memorialist.