early 15c., "written record," from Anglo-French memorie "note, memorandum, something written to be kept in mind" (early 15c., Old French memoire), from Latin memoria (from PIE root *(s)mer- (1) "to remember"). The more specific sense of "a notice or essay relating to something within the writer's own memory or knowledge" is from 17c. Meaning "person's written account of his or her life" is from 1670s. Related: Memoirist.
Biography, Memoir. When there is a difference between these words, it may be that memoir indicates a less complete or minute account of a person's life, or it may be that the person himself records his own recollections of the past, especially as connected with his own life; in the latter case memoir should be in the plural. [Century Dictionary]
"personal record of events, narrative of the facts or events of the life of a person or a phase of history written from personal knowledge or observation upon points about which the writer is specially informed," 1650s, plural of memoir.
early 15c., "series or collection of comments," from Medieval Latin commentarius "notebook, annotation; diary, memoir," noun use of adjective, "relating to comments," from Late Latin commentum ""comment, interpretation" (see comment (n.)). Perhaps the Medieval Latin noun is short for volumen commentarium. Especially "explanation of difficult and obscure passages in a book or other writing" (1530s). Meaning "historical narrative" is from c. 1600. Meaning "description of some public event" is from 1927.
The propensity which leads an insane person to accomplish his purpose by burning, has been considered to merit particular notice, and to constitute a variety of monomania. Dr. Marc, of France, has published a memoir on the subject; he gives the name of pyromania to it, and considers that, like other insane propensities, it may be the result of instinct, or it may be the result of delusion—reasoning upon erroneous principles. [Alexander Morrison, M.D., "The Physiognomy of Mental Diseases," London, 1840]
An older word for it was incendiarism.
late 14c., the Hebrew word shibboleth, meaning "flood, stream," also "ear of corn;" in Judges xii.4-6. It was the password used by the Gileadites to distinguish their own men from fleeing Ephraimites, because Ephraimites could not pronounce the -sh- sound. Hence the figurative sense of "watchword" (first recorded 1630s), which evolved by 1862 to "outmoded slogan still adhered to." A similar test-word was cicera "chick pease," used by the Italians to identify the French (who could not pronounce it correctly) during the massacre called the Sicilian Vespers (1282).
During training exercises on Pavuvu and Guadalcanal, the need to improve battlefield security is to be implemented not by a simple password, but by an identification procedure described as "sign and countersign." The ground rules are to sequentially interrogate an unknown friend or foe with the name of an automobile, preferably one with an "L" in its vocalization. The response is to be a cognomen for another automobile uttered in the same manner. This insures the "friend" entering our lines will reply with the correct countersign in a dialect distinctly American; call out "Cadiwac" or "Chryswer," and you're dead. [Perry Pollins, "Tales of a Feather Merchant: The World War II Memoir of a Marine Radioman," 2006]