late 13c., "recollection (of someone or something); remembrance, awareness or consciousness (of someone or something)," also "fame, renown, reputation;" from Anglo-French memorie (Old French memoire, 11c., "mind, memory, remembrance; memorial, record") and directly from Latin memoria "memory, remembrance, faculty of remembering," abstract noun from memor "mindful, remembering," from PIE root *(s)mer- (1) "to remember."
Sense of "commemoration" (of someone or something) is from c. 1300. Meaning "faculty of remembering; the mental capacity of retaining unconscious traces of conscious impressions or states, and of recalling these to consciousness in relation to the past," is late 14c. in English. Meaning "length of time included in the consciousness or observation of an individual" is from 1520s.
I am grown old and my memory is not as active as it used to be. When I was younger I could remember anything, whether it had happened or not; but my faculties are decaying now and soon I shall be so I cannot remember any but the things that never happened. It is sad to go to pieces like this, but we all have to do it. ["Mark Twain," "Autobiography"]
Meaning "that which is remembered; anything fixed in or recalled to the mind" is by 1817, though the correctness of this use was disputed in 19c. The word was extended, with more or less of figurativeness, in 19c. to analogous physical processes. Computer sense, "device which stores information," is from 1946. Related: Memories.
Proto-Indo-European root meaning "to remember."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit smarati "remembers;" Avestan mimara "mindful;" Greek merimna "care, thought," mermeros "causing anxiety, mischievous, baneful;" Latin memoria "memory, remembrance, faculty of remembering," memor "mindful, remembering;" Serbo-Croatian mariti "to care for;" Welsh marth "sadness, anxiety;" Old Norse Mimir, name of the giant who guards the Well of Wisdom; Old English gemimor "known," murnan "to mourn, remember sorrowfully;" Dutch mijmeren "to ponder."
"pertaining to memory," 1898, from Greek mnesikos "of memory," from mnesis "memory" (see mnemonic).
1753, "aiding the memory, intended to assist the memory;" 1825, "pertaining to the memory," a back-formation from mnemonics, or from a Latinized form of Greek mnēmonikos "of or pertaining to memory," from mnēmōn (genitive mnēmonos) "remembering, mindful," from mnēmē "memory, a remembrance, record, an epitaph; memory as a mental faculty," from base of mnasthai "remember," from PIE root *men- (1) "to think." The noun meaning "mnemonic device" is from 1858. Related: Mnemonical (1660s).
late 14c., "memorable, excellent," also "remembered, committed to memory," from Old French memorial "mindful of, remembering" (Modern French mémorial), and directly from Latin memorialis "of or belonging to memory," from memoria "memory" (from PIE root *(s)mer- (1) "to remember"). From mid-15c. as "preservative of memory, serving for commemoration."
A Middle English word for "having to do with memory" was memorative (late 14c.), from Old French memoratif, from Latin memorativus. Though useful, it apparently has not survived.