1670s, nicompoop; modern form from 1713. Despite similarity [noted by Johnson] to Latin legal phrase non compos mentis "insane, mentally incompetent" (c. 1600), the connection is denied by the OED's etymologists because the earliest forms lack the second -n-. Weekley thinks first element may be a proper name, and cites Nicodemus, which he says was used in French for "a fool," or Nicholas. Klein says it is probably an invented word. Century Dictionary has no objection to the non compos mentis theory.
"to dupe, tease, fool," by 1930, apparently from rib (n.), which is attested by 1929 in a slang sense of "a joke," perhaps a figurative use of poking someone in the ribs (rib-digging "light-heated banter" is attested by 1925).
Earlier it meant "to plow land so as to leave a space between furrows (1735) and "to clean (flax) with a rib" (early 14c.), a special tool for that job, which is probably an extended sense of rib (n.). Compare Middle Low German ribbeisern ("rib-iron"), a tool for cleaning flax. Related: Ribbed; ribbing.
ME chubbe ... was also used of a "lazy, spiritless fellow; a rustic, simpleton; dolt, fool" (1558), whilst Bailey has "Chub, a Jolt-head, a great-headed, full-cheeked Fellow," a description reminiscent of that of the chevin, another name for the chub ... Thus the nickname may have meant either "short and thick, dumpy like a chub," or "of the nature of a chub, dull and clownish." ["Dictionary of English Surnames"]
Meaning "to put or shift off (something) by pretense" is from 1650s; to fob (someone) off "put him off deceitfully" is from 1590s. Related: Fobbed; fobbing.
German Pavian "baboon" is from Dutch baviaan, from Middle Dutch baubijn, a borrowing of the Old French word. Century Dictionary says Arabic maimun probably is from the European words.
Used in Middle English to translate Latin animal. Replaced Old English deor (see deer) as the generic word for "wild creature," only to be ousted 16c. by animal.
mid-15c., mokken, "make fun of," also "to trick, delude, make a fool of; treat with scorn, treat derisively or contemptuously;" from Old French mocquer "deride, jeer," a word of unknown origin. Perhaps from Vulgar Latin *muccare "to blow the nose" (as a derisive gesture), from Latin mucus; or possibly from Middle Dutch mocken "to mumble" or Middle Low German mucken "grumble." Perhaps ultimately it is imitative of such speech. Related: Mocked; mocking. Replaced Old English bysmerian. The sense of "imitate, simulate, resemble closely" (1590s, as in mockingbird ; also see mock (adj.)) is from the notion of derisive imitation.
1910, medical Latin, "one of the highest class of feeble-minded persons," from Greek (Attic) mōron, neuter of mōros "foolish, dull, sluggish, stupid," a word of uncertain origin. The former connection with Sanskrit murah "idiotic" (see moratorium) is in doubt. Latin morus "foolish" is a loan-word from Greek.
Adopted by the American Association for the Study of the Feeble-minded with a technical definition "adult with a mental age between 8 and 12;" used as an insult since 1922 and subsequently dropped from technical use. Linnæus had introduced morisis "idiocy."
The feeble-minded may be divided into: (1) Those who are totally arrested before the age of three so that they show the attainment of a two-year-old child or less; these are the idiots. (2) Those so retarded that they become permanently arrested between the ages of three and seven; these are imbeciles. (3) Those so retarded that they become arrested between the ages of seven and twelve; these were formerly called feeble-minded, the same term that is applied to the whole group. We are now proposing to call them morons, this word being the Greek for "fool." The English word "fool" as formerly used describes exactly this grade of child—one who is deficient in judgment or sense. [Henry H. Goddard, in "Journal of Proceedings and Addresses" of the National Education Association of the United States, July 1910]
"foolish person," 1953, OED suggests from earlier cant slang nigmenog "a very silly fellow" (1700). Compare Australian and dialectal ning-nong "fool" (1832). The word turns up in various apparently unrelated contexts in late 19c.-early 20c. Wright's "Dictionary of Obsolete and Provincial Words" (1886) has nig-nog as a verb for "to fuck." It also was the name of a fictitious patent medicine that "cures all nervous ailments," etc. in a humor story by Edgar Wallace originally published in 1923. As a term of abuse for a black person (by 1959), a shortened and reduplicated form of nigger.