late 14c., "a proposition inadvertently proved in proving another," from Late Latin corollarium "a deduction, consequence," from Latin corollarium, originally "money paid for a garland," hence "gift, gratuity, something extra;" and in logic, "a proposition proved from another that has been proved." From corolla "small garland," diminutive of corona "a crown" (see crown (n.)).

Also in Middle English "a follower, a sycophant" (late 14c.). As an adjective, "of the nature of a corollary," mid-15c.

title of a county or municipal officer with certain duties, mid-14c. (mid-13c. as a surname), corouner, from Anglo-French curuner, from Anglo-Latin custos placitorum coronae (late 12c.), originally the title of the officer with the duty of protecting the private property of the royal family, from Latin corona, literally "crown" (see crown (n.)).

In the Middle English period an elected county or borough officer charged with the supervision of pleas of the Crown and the administration of criminal justice.  The duties of the office gradually narrowed and by 17c. the chief function was to determine the cause of death in cases not obviously natural.

early 12c., coroune, croune, "royal crown, ornament for the head as a symbol of sovereignty," from Anglo-French coroune, Old French corone (13c., Modern French couronne) and directly from Latin corona "crown," originally "wreath, garland," related to Greek korōnē "anything curved, a kind of crown," according to Watkins from a suffixed form of PIE root *sker- (2) "to turn, bend."

But Beekes considers the "crown" sense as derived from the formally identical Greek word korōnē "crow" (see raven), which, he says, was used metaphorically "of all kinds of curved or hook-formed objects." "Moreover," he writes, "the metaphorical use of [korōnē] 'crow' is nothing remarkable given the use of its cognates ...; the metaphors may have originated from the shape of the beak or the claws of the bird." Compare Latin corax "crow," also "a hooked engine of war," French corbeau "raven," also "cantilever;" English crowbar, etc. 

Old English used corona, directly from Latin. Figuratively, "regal power," from c. 1200. From late 14c. as "a crowning honor or distinction." From c. 1300 as "top part of the skull or head;" from 1670s as "top of a hat." From 1804 as "part of a tooth which appears above the gum."

Extended late 14c. to "coin bearing the imprint of a crown or a crowned head," especially the British silver 5-shilling piece. Also the name of monetary units in Iceland, Sweden (krona), Norway, Denmark (krone), and formerly in German Empire and Austria-Hungary (krone). Crown of thorns was late Old English þornene crune.

"chief commander of a regiment of troops," 1540s, coronell, from Middle French coronel (16c.), modified by dissimilation from Italian colonnella "commander of the column of soldiers at the head of a regiment," from compagna colonella "little column company," from Latin columna "pillar," collateral form of columen "top, summit," from PIE root *kel- (2) "to be prominent; hill."

The French spelling was reformed late 16c. English spelling was modified 1580s in learned writing to conform with the Italian form (via translations of Italian military manuals), and pronunciations with "r" and "l" coexisted until c. 1650, but the earlier pronunciation prevailed. Spanish and Portuguese  coronel, from Italian, show similar evolution by dissimilation and perhaps by influence of corona. Abbreviation col. is attested by 1707.

also *ker-, Proto-Indo-European root meaning "to turn, bend."

It forms all or part of: arrange; circa; circadian; circle; circuit; circum-; circumcision; circumflex; circumnavigate; circumscribe; circumspect; circumstance; circus; cirque; corona; crepe; crest; crinoline; crisp; crown;  curb; curvature; curve; derange;  flounce (n.) "deep ruffle on the skirt of a dress;" krone; ring (n.1) "circular band;" ranch; range; ranger; rank (n.) "row, line series;" research; recherche; ridge; rink; rucksack; search; shrink.

It is the hypothetical source of/evidence for its existence is provided by: Latin curvus "bent, curved," crispus "curly;" Old Church Slavonic kragu "circle;" perhaps Greek kirkos "ring," koronos "curved;" Old English hring "ring, small circlet."

type of infectious disease, now known to be caused by a virus, usually occurring as an epidemic, with symptoms similar to a severe cold along with high fever and rapid prostration, 1743, borrowed (during an outbreak of the disease in Europe), from Italian influenza "influenza, epidemic," originally "visitation, influence (of the stars)," from Medieval Latin influentia in the astrological sense (see influence).

AN Article from Rome informs us that a Sort of Plague has broke out there, which destroys Abundance of their People, and they call it the Influenza. [The Gentleman's Magazine, April 1743]

Used in Italian for diseases at least since 1504 (as in influenza di febbre scarlattina "scarlet fever") on notion of astral, occult, or atmospheric influence. The 1743 outbreak began in Italy. Often applied since mid-19c. to severe colds.

1800, used by British physician Edward Jenner (1749-1823) for the technique he publicized of preventing smallpox by injecting people with the similar but much milder cowpox virus (variolae vaccinae), from vaccine (adj.) "pertaining to cows, from cows" (1798), from Latin vaccinus "from cows," from vacca "cow," a word of uncertain origin. A mild case of cowpox rendered one immune thereafter to smallpox. "The use of the term for diseases other than smallpox is due to Pasteur" [OED].

The earlier 18c. method of smallpox protection in England was by a kind of inoculation called  variolation (from variola, the medical Latin word for "smallpox"). There are two forms of smallpox: a minor one that killed 2% or less of the people who got it, and a virulent form that had about a 30% mortality rate and typically left survivors with severe scarring and often blinded them. Those who got the minor form were noted to be immune thereafter to the worse. Doctors would deliberately infect healthy young patients with a local dose of the minor smallpox, usually resulting in a mild case of it at worst, to render them immune to the more deadly form. Jenner's method was safer, as it involved no smallpox exposure.

c. 1200, poisoun, "a deadly potion or substance," also figuratively, "spiritually corrupting ideas; evil intentions," from Old French poison, puison (12c., Modern French poison) "a drink," especially a medical drink, later "a (magic) potion, poisonous drink" (14c.), from Latin potionem (nominative potio) "a drinking, a drink," also "poisonous drink" (Cicero), from potare "to drink" (from PIE root *po(i)- "to drink").

A doublet of potion. For similar form evolution from Latin to French, compare raison from rationem, trahison from traditionem. The more usual Indo-European word for this is represented in English by virus. The Old English word was ator (see attercop) or lybb (cognate with Old Norse lyf "medicinal herbs;" see leaf (n.)).

For sense evolution, compare Old French enerber, enherber "to kill with poisonous plants." In many Germanic languages "poison" is named by a word equivalent to English gift (such as Old High German gift, German Gift, Danish and Swedish gift; Dutch gift, vergift). This shift might have been partly euphemistic, partly by influence of Greek dosis "a portion prescribed," literally "a giving," used by Galen and other Greek physicians to mean an amount of medicine (see dose (n.)).

Of persons detested or regarded as exerting baleful influence, by 1910. The slang meaning "alcoholic drink" is by 1805 in American English (potus as a past-participle adjective in Latin meant "drunken").

As an adjective from 1520s; with plant names from 18c. Poison ivy is recorded by 1784 for a shrub-vine of North America causing an itching rash on contact; poison oak for poison ivy or related species is by 1743. Poison sumac (1817), causing an even more severe rash, is a swamp-border tree noted for the brilliant red of its leaves in fall. Poison gas is recorded from 1915. Poison-pen (letter) was popularized 1913 by a notorious criminal case in Pennsylvania, U.S.; the phrase dates to 1898.