Etymology
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sumac (n.)

also sumach, c. 1300, "preparation of dried, chopped leaves of a plant of the genus Rhus" (used in tanning and dyeing and as an astringent), from Old French sumac (13c.), from Medieval Latin sumach, from Arabic summaq, from Syrian summaq "red." Of the tree itself from 1540s; later applied to a North American plant species.

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poison (n.)
Origin and meaning of poison

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.

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poison (v.)
Origin and meaning of poison

"to give poison to; add poison to; kill with poison," c. 1300, poisonen, from Old French poisonner "to give to drink," and directly from poison (n.). Figuratively, "to corrupt," from late 14c. Related: Poisoned; poisoning.

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counter-poison (n.)

also counterpoison, "antidote," 1570s, from counter- + poison (n.).

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rat-poison (n.)

"something used to poison rats with," especially arsenic, 1799, from rat (n.) + poison (n.).

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poisonous (adj.)

"having the properties of a poison; containing poison," 1570s, from poison (n.) + -ous. Failed rivals were poisonsome (1590s), poisonful (1550s), poisony (1590s). Earlier poisoned was used (late 15c.). Related: Poisonously; poisonousness. Compare venomous.

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antitoxic (n.)

"substance which counteracts a poison," 1860; from anti- "against" + toxic. As an adjective, "counteracting a poison," from 1862.

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intoxicate (v.)

mid-15c., "to poison" (obsolete), from Medieval Latin intoxicatus, past participle of intoxicare "to poison," from in- "in" (from PIE root *en "in") + Latin toxicare "to poison," from toxicum "poison" (see toxic). Meaning "make drunk" first recorded 1570s (implied in intoxicated). Figurative sense "excite to a high pitch of feeling" is attested from 1590s. Related: Intoxicating.

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pharmaco- 

word-forming element meaning "drug, medicine," also "poison," from Latinized form of Greek pharmakon "drug, poison" (see pharmacy).

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virus (n.)
Origin and meaning of virus

late 14c., "poisonous substance" (a sense now archaic), from Latin virus "poison, sap of plants, slimy liquid, a potent juice," from Proto-Italic *weis-o-(s-) "poison," which is probably from a PIE root *ueis-, perhaps originally meaning "to melt away, to flow," used of foul or malodorous fluids, but with specialization in some languages to "poisonous fluid" (source also of Sanskrit visam "venom, poison," visah "poisonous;" Avestan vish- "poison;" Latin viscum "sticky substance, birdlime;" Greek ios "poison," ixos "mistletoe, birdlime;" Old Church Slavonic višnja "cherry;" Old Irish fi "poison;" Welsh gwy "poison").

The meaning "agent that causes infectious disease" emerged by 1790s gradually out of the earlier use in reference to venereal disease (by 1728); the modern scientific use dates to the 1880s. The computer sense is from 1972.

VIRUS (among Physicians) a kind of watery stinking Matter, which issues out of Ulcers, being endued with eating and malignant Qualities. [Bailey's dictionary, 1770]
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