"stubborn in adhering to one's own course, unyielding," late 14c., from Latin obstinatus "resolute, resolved, determined, inflexible, stubborn," past participle of obstinare "persist, stand stubbornly, set one's mind on," from ob "by" (see ob-) + stinare (related to stare "stand"), from PIE *ste-no-, from root *sta- "to stand, make or be firm." Related: Obstinately.
"stiff, unyielding, inflexible, firm, not easily bent," early 15c., from Latin rigidus "hard, stiff, rough, severe," from rigēre "be stiff" (from PIE root *reig- "stretch; be stretched; be stiff"). Related: Rigidly. As a verb, "to make rigid," rigidize is attested by 1944 in U.S. military and commercial use in reference to metals; earlier was rigidify (1842), rigidification.
1660s, cast iron, from iron (n.) + cast (adj.) "made by melting and being left to harden in a mold" (1530s), past-participle adjective from cast (v.) in its sense "to throw something (in a particular way)," c. 1300, especially "form metal into a shape by pouring it molten" (1510s). From 1690s as an adjective, "made of cast-iron;" figurative sense of "inflexible, unyielding" is from 1830.
1640s, "downy, fuzzy," later "flimsy, unsubstantial" (1660s), of unknown origin; one theory is that it is a corruption of Silesia, the German region, where thin linen or cotton fabric was made for export. Silesia in reference to cloth is attested in English from 1670s; and sleazy as an abbreviated form is attested from 1670), but OED is against this. Sense of "sordid" is from 1941. Related: Sleazily; sleaziness.
A day is a more magnificent cloth than any muslin, the mechanism that makes it is infinitely cunninger, and you shall not conceal the sleazy, fraudulent, rotten hours you have slipped into the piece, nor fear that any honest thread, or straighter steel, or more inflexible shaft, will not testify in the web. [Emerson, "The Conduct of Life," 1860]
mid-14c., diamaunt, diamond, "extremely hard and refractive precious stone made of pure or nearly pure carbon," from Old French diamant, from Medieval Latin diamantem (nominative diamas), from Vulgar Latin *adiamantem (which was subsequently altered by influence of the many Greek words in dia-), from Latin adamantem (nominative adamans) "the hardest metal," later, "diamond," from Greek adamas (genitive adamantos), name of a hypothetical hardest material, noun use of an adjective meaning "unbreakable, inflexible," a word of uncertain origin (see adamant (n.)).
From early 15c. as "person of great worth" (a sense also in Latin). From late 15c. as "geometric figure of four equal straight lines forming two acute and two obtuse angles." From 1590s as "playing-card stamped with one or more red diamonds." In baseball, "square space enclosed within the four bases," is American English, by 1875. As an adjective "resembling, consisting of, or set with diamonds," from 1550s.
"government by bureaus," especially "tyrannical officialdom," excessive multiplication of administrative bureaus and concentration of power in them, in reference to their tendency to interfere in private matters and be inefficient and inflexible, 1818, from French bureaucratie, coined by French economist Jean Claude Marie Vincent de Gournay (1712-1759) on model of democratie, aristocratie, from bureau "office," literally "desk" (see bureau) + Greek suffix -kratia denoting "power of" (see -cracy).
That vast net-work of administrative tyranny ... that system of bureaucracy, which leaves no free agent in all France, except for the man at Paris who pulls the wires. [J.S. Mill, Westminster Review vol. xxviii, 1837]
bureaucrat, &c. The formation is so barbarous that all attempt at self-respect in pronunciation may perhaps as well be abandoned. [Fowler]
It is perhaps literally "invincible, indomitable," from a- "not" (see a- (3)) + daman "to conquer, to tame," from PIE root *deme- "to constrain, force, break (horses)" (see tame (adj.)). "But semantically, the etymology is rather strange," according to Beekes, who suggests it might be a foreign word altered in Greek by folk etymology, and compares Akkadian (Semitic) adamu.
Applied in antiquity to a metal resembling gold (Plato), white sapphire (Pliny), magnet (Ovid, perhaps through confusion with Latin adamare "to love passionately"), steel, emery stone, and especially diamond, which is a variant of this word. "The name has thus always been of indefinite and fluctuating sense" [Century Dictionary].
element meaning "into, in, on, upon" (also im-, il-, ir- by assimilation of -n- with following consonant), from Latin in- "in," from PIE root *en "in."
In Old French (and hence in Middle English) this often became en-, which in English had a strong tendency to revert to Latin in-, but not always, which accounts for pairs such as enquire/inquire. There was a native form, which in West Saxon usually appeared as on- (as in Old English onliehtan "to enlighten"), and some of those verbs survived into Middle English (such as inwrite "to inscribe"), but all now seem to be extinct.
Not related to in- (1) "not," which also was a common prefix in Latin, causing confusion: to the Romans impressus could mean "pressed" or "unpressed;" inaudire meant "to hear," but inauditus meant "unheard of;" in Late Latin investigabilis could mean "that may be searched into" or "that cannot be searched into." Latin invocatus was "uncalled, uninvited," but invocare was "to call, appeal to."
The trouble has continued in English; the hesitation over what is meant by inflammable being a commonly cited example. Implume (1610s) meant "to feather," but implumed (c. 1600) meant "unfeathered." Impliable can mean "capable of being implied" (1865) or "inflexible" (1734). Impartible in 17c. could mean "incapable of being divided" or "capable of being imparted." Impassionate can be "free from passion" or it can mean "strongly stirred by passion." Inanimate (adj.) is "lifeless," but Donne uses inanimate (v.) to mean "infuse with life or vigor." Irruption is "a breaking in," but irruptible is "unbreakable."
In addition to improve "use to one's profit," Middle English also had a verb improve meaning "to disprove" (15c.). To inculpate is "to accuse," but inculpable means "not culpable, free from blame." Infestive has meant "troublesome, annoying" (1560s, from infest) and "not festive" (1620s). In Middle English inflexible could mean "incapable of being bent" or "capable of being swayed or moved." In 17c., informed could mean "current in information," formed, animated," or "unformed, formless" ("This was an awkward use" [OED]). Inhabited has meant "dwelt in" (1560s) and "uninhabited" (1610s); inhabitable likewise has been used on opposite senses, a confusion that goes back to Late Latin.