Etymology
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probability (n.)

mid-15c., probabilite, "likelihood of being realized, appearance of truth, quality of being probable," from Old French probabilite (14c.) and directly from Latin probabilitatem (nominative probabilitas) "credibility, probability," from probabilis (see probable).

Meaning "something likely to be true" is from 1570s; mathematical sense is from 1718, "frequency with which a proposition similar to the one in question is found true in the course of experience."

In weather forecasting, probabilities was used in U.S. from 1869 and adopted in the official weather forecasts of the United States Signal Service; hence Old Probabilities, a humorous name for the chief signal officer of the Signal Service Bureau (by 1875).

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likeliness (n.)
late 14c., "resemblance," also "probability," from likely + -ness.
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likelihood (n.)
late 14c., "resemblance, similarity," from likely + -hood. Meaning "probability, state of being like or probable" is from mid-15c.
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probabilistic (adj.)

1855, in Catholic theology (see probabilism), from probabilist "one who holds the doctrine of probabilism" (1650s, from French probabiliste, 17c., from Latin probabilis, see probable) + -ic. Meaning "pertaining to probability, involving chance variations" is from 1951.

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presumptive (adj.)

"speculative, based on presumption or probability," mid-15c., from Medieval Latin presumptivus, from Late Latin praesumptivus, from Latin praesumpt- past-participle stem of praesumere (see presume). The heir presumptive (1620s) is "presumed" to be the heir if the heir apparent is unavailable. Related: Presumptively.

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aroint (v.)
intransitive verb, c. 1600, used by Shakespeare (only in imperative, aroint thee! "begone!"), obsolete and of obscure origin. "[T]he subject of numerous conjectures, none of which can be said to have even a prima facie probability." [OED]
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chance (n.)

c. 1300, "something that takes place, what happens, an occurrence" (good or bad, but more often bad), especially one that is unexpected, unforeseen, or beyond human control, also "one's luck, lot, or fortune," good or bad, in a positive sense "opportunity, favorable contingency;" also "contingent or unexpected event, something that may or may not come about or be realized," from Old French cheance "accident, chance, fortune, luck, situation, the falling of dice" (12c., Modern French chance), from Vulgar Latin *cadentia "that which falls out," a term used in dice, from neuter plural of Latin cadens, present participle of cadere "to fall," from PIE root *kad- "to fall."

In English frequently in plural, chances. The word's notions of "opportunity" and "randomness" are as old as the record of it in English and now all but crowd out its original notion of "mere occurrence." Meaning "fortuity, absence of any cause why an event should happen or turn out as it does, variability viewed as a real agent" is from c. 1400.

Chance is equivalent to the mathematical concept of probability, which is a precisely measurable factor enabling the accurate prediction of average outcomes over long runs of random events — the longer the run, the more accurate the predictions. Luck is at best a platitude and at worst a superstition. [David Partlett, "A History of Card Games"]

Main chance "probability that offers greatest advantage," hence "thing of most importance" is from 1570s. Mathematical sense "probability, likelihood of a certain outcome" is from 1778, hence the odds-making sense "balanced probability of gain or loss." To stand a chance (or not) is from 1796. To take (one's) chances "accept what happens" (early 14c.) is from the old, neutral sense; to take a chance/take chances is originally (by 1814) "participate in a raffle or lottery or game;" extended sense of "take a risk" is by 1826.

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spinet (n.)

1660s, spinette, "small harpsichord," from French espinette (16c., Modern French épinette), from Italian spinetta, said by Scaliger to be a diminutive of spina "thorn, spine," from Latin spina "thorn" (see spine), so called because the strings were plucked with thorn-like quills [Barnhart]. The other theory (favored by Klein and assigned "greater probability" by OED) dates to early 17c. and claims the word is from the name of the Venetian inventor, Giovanni Spinetti (fl. c. 1503). As "small, upright piano" from 1936.

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petitio principii 

Latin, from petitio "petition" (see petition (n.)) + genitive of principium (see principle (n.)). It translates Greek to en arkhē aiteisthai "an assumption at the outset."

In logic, the assumption of that which in the beginning was set forth to be proved; begging the question: a fallacy or fault of reasoning belonging to argumentations whose conclusions really follow from their premises, either necessarily or with the degree of probability pretended, the fault consisting in the assumption of a premise which no person holding the antagonistic views will admit. [Century Dictionary]
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Monte Carlo 

resort town, capital of Monaco, Italian, literally "Charles's Mountain," founded 1866 and named for Charles III of Monaco (1818-1889). The car rally there dates to 1911. The Monte Carlo fallacy (by 1957) was named for the town's famous gambling casinos; it is the fallacy of thinking that the probability of a particular outcome rises with the successive number of opposite outcomes. Contrary to the Monte Carlo fallacy, if the roulette wheel stops on black 99 times in a row, the chances that the 100th spin will be red are still just under 50-50. 

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