Etymology
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snake oil (n.)

1927 as "phony remedy," American English, from the use of oil derived from the fat of snakes (especially the rattlesnake) as a folk remedy in the rural regions of the U.S. Snake oil in this sense is attested by 1858. It was a folk remedy for rheumatism and gout in Georgia, but a cure for deafness in rural Pennsylvania. Professional pharmacy journals began to condemn it early 20c., not because it was quackery but because products sold under the name had no real snake oil in them.

What is known as snake oil is usually a combination which is handed out by the dealer to satisfy the demand of some credulous customer. A genuine oil of course is that which is obtained by "trying out" the fat of a snake, usually the rattlesnake, and to preserve their faces druggists sometimes employ a small proportion of such oil in preparing the weird mixtures dispensed by them. [The Practical Druggist, July 1912]
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snake (v.)
1650s, "to twist or wind (hair) into the form of a snake," from snake (n.). The intransitive sense of "to move like a snake" is attested from 1848; that of "to wind or twist like a snake" (of roads, etc.) is from 1875. Related: Snaked; snaking.
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snake (n.)

Old English snaca, from Proto-Germanic *snakon (source also of Old Norse snakr "snake," Swedish snok, German Schnake "ring snake"), from PIE root *sneg- "to crawl, creeping thing" (source also of Old Irish snaighim "to creep," Lithuanian snakė "snail," Old High German snahhan "to creep"). In Modern English, gradually replacing serpent in popular use.

Traditionally applied to the British serpent, as distinguished from the poisonous adder. Meaning "treacherous person" first recorded 1580s (compare Old Church Slavonic gadu "reptile," gadinu "foul, hateful"). Applied from 17c. to various snake-like devices and appliances. Snakes! as an exclamation is from 1839.

Snake eyes in crap-shooting sense is from 1919. Snake-bitten "unlucky" is sports slang from 1957, from a literal sense, perhaps suggesting one doomed by being poisoned. The game of Snakes and Ladders is attested from 1907. Snake charmer is from 1813. Snake pit is from 1883, as a supposed primitive test of truth or courage; figurative sense is from 1941. Phrase snake in the grass is from Virgil's Latet anguis in herba [Ecl. III:93].

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oil (n.)

late 12c., "olive oil," from Anglo-French and Old North French olie, from Old French oile, uile "oil" (12c., Modern French huile), from Latin oleum "oil, olive oil" (source of Spanish, Italian olio), from Greek elaion "olive tree," from elaia (see olive).

Nearly all the European languages' words for "oil" (Croatian ulje, Polish olej, Hungarian olaj, Albanian uli, Lithuanian alejus, etc.) are from the Greek word; the Germanic (except Gothic) and Celtic one coming from Greek via Latin: Old English æle, Dutch olie, German Öl, Welsh olew, Gaelic uill, etc. 

In English it meant "olive oil" exclusively till c. 1300, when the word began to be extended to any fatty, greasy liquid substance (usually flammable and insoluble in water). Often especially "oil as burned in a lamp to afford light" (as in midnight oil, symbolizing late work). Use for "petroleum" is recorded from 1520s but not common until 19c.

The artist's oils (1660s), short for oil-color (1530s), are paints made by grinding pigment in oil. Oil-painting is attested from 1782.  The ocean-going oil-tanker is from 1900; oil-spill is from 1970. As a condiment, oil and vinegar is attested from 1620s. The figurative expression pour oil upon the waters "appease strife or disturbance" is by 1840, from an ancient trick of sailors.

Another historical illustration which involves monolayers, was when sailors poured oil on the sea in order to calm 'troubled waters' and so protect their ship. This worked by wave damping or, more precisely, by preventing small ripples from forming in the first place so that the wind could have no effect on them. [J. Lyklema, "Fundamentals of Interface and Colloid Science," Academic Press, 2000]

The phenomenon depends on what are called Marangoni effects; Benjamin Franklin experimented with it in 1765.

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oil (v.)

"to smear or rub with oil or ointment," mid-15c., oilen, from oil (n.). Later especially "to lubricate (machinery)." Related: Oiled; oiling. An Old English verb in this sense was besmyrian.

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oil-skin (n.)

also oilskin, "cloth of cotton, linen, etc., prepared with oil to make it water-proof," 1816, from oil (n.) + skin (n.).

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corn-snake (n.)

popular name of a type of large but harmless rat-snake of the southeastern and central U.S., often found in cornfields, 1670s, from corn (n.1) + snake (n.).

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milk-snake (n.)

"A handsome and harmless serpent" [Century Dictionary], one of the larger snakes of the U.S., common in many states, by 1812, from milk (n.) + snake (n.). Also called chicken-snake (attested by 1793), house-snake, and thunder-and-lightning snake.

It [the milk-snake] sometimes in this county has been known to enter a grist-mill and remain a length of time for the apparent purpose of feeding on the mice which were there attainable. It is probable this is one principal object of his frequenting dwelling houses, and not always for the purpose of obtaining milk, as is generally supposed. [The American Journal of Science and Arts, April 1844]
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rat-snake (n.)

"snake which kills rats," 1818, from rat (n.) + snake (n.).

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oil-cloth (n.)

also oilcloth, 1690s, "cotton or a similar fabric waterproofed with oil," from oil (n.) + cloth. In reference to an oil-treated canvas used as a cheap floor covering, 1796.

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