Etymology
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function (n.)

1530s, "one's proper work or purpose; power of acting in a specific proper way," from French fonction (16c.) and directly from Latin functionem (nominative functio) "a performance, an execution," noun of action from funct-, past-participle stem of fungi "perform, execute, discharge," from PIE *bhung- "be of use, be used" (source also of Sanskrit bhunjate "to benefit, make benefit, atone," Armenian bowcanem "to feed," Old Irish bongaid "to break, harvest"), which is perhaps related to root *bhrug- "to enjoy." Meaning "official ceremony" is from 1630s, originally in church use. Use in mathematics probably was begun by Leibnitz (1692). In reference to computer operations, 1947.

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satisfaction (n.)

early 14c., satisfaccioun, "performance by a penitent of an act set forth by a priest or other Church authority to atone for sin," from Old French satisfaction (12c.), from Latin satisfactionem (nominative satisfactio) "a satisfying of a creditor," noun of action from past-participle stem of satisfacere "discharge fully, comply with, make amends," literally "to do enough" (see satisfy).

Originally religious and involving such acts as expiatory prayer, self-denial, charity. The sense of "contentment, appeasement" is from late 14c. but was not common before 16c. The sense of "action of gratifying" (an appetite or desire) also is from late 14c.; that of "gratified or contented feeling or state of mind" is from late 15c. (Caxton).

From 1580s as "information that answers a person's demands or removes doubt." Hence the specific sense "opportunity of satisfying one's honor by accepting a duel, etc., with the aggrieved person" (c. 1600).

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pain (n.)

late 13c., peine, "the agony suffered by Christ;" c. 1300, "punishment," especially for a crime, "legal punishment of any sort" (including fines and monetary penalties); also "condition one feels when hurt, opposite of pleasure," including mental or emotional suffering, grief, distress; from Old French peine "difficulty, woe, suffering, punishment, Hell's torments" (11c.), from Latin poena "punishment, penalty, retribution, indemnification" (in Late Latin also "torment, hardship, suffering"), from Greek poinē "retribution, penalty, quit-money for spilled blood," from PIE *kwei- "to pay, atone, compensate" (see penal).

The early "punishment" sense in English survives in phrase on pain of death. Also c. 1300 the word was used for the torments of eternal damnation after death. The sense of "exertion, effort" is from late 14c.; pains "great care taken (for some purpose), exertion or trouble taken in doing something" is recorded from 1520s.

 Phrase give (someone) a pain "be annoying and irritating" is by 1895; as a noun, localized as pain in the neck (1924) and pain in the ass (1934), though this last might have gone long unrecorded and be the original sense and the others euphemisms. First record of pain-killer "drug or herb that reduces pain" is by 1845.

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good (adj.)
Origin and meaning of good

Old English gōd (with a long "o") "excellent, fine; valuable; desirable, favorable, beneficial; full, entire, complete;" of abstractions, actions, etc., "beneficial, effective; righteous, pious;" of persons or souls, "righteous, pious, virtuous;" probably originally "having the right or desirable quality," from Proto-Germanic *gōda- "fitting, suitable" (source also of Old Frisian god, Old Saxon gōd, Old Norse goðr, Middle Dutch goed, Dutch goed, Old High German guot, German gut, Gothic goþs). A word of uncertain etymology, perhaps originally "fit, adequate, belonging together," from PIE root *ghedh- "to unite, be associated, suitable" (source also of Sanskrit gadh- "seize (booty)," Old Church Slavonic godu "favorable time," Russian godnyi "fit, suitable," Lithuanian goda "honor," Old English gædrian "to gather, to take up together").

Irregular comparative and superlative (better, best) reflect a widespread pattern in words for "good," as in Latin bonus, melior, optimus.

Sense of "kind, benevolent" is from late Old English in reference to persons or God, from mid-14c. of actions. Middle English sense of "holy" is preserved in Good Friday. That of "friendly, gracious" is from c. 1200. Meaning "fortunate, prosperous, favorable" was in late Old English. As an expression of satisfaction, from early 15c. Of persons, "skilled (at a profession or occupation), expert," in late Old English, now typically with at; in Middle English with of or to. Of children, "well-behaved," by 1690s. Of money, "not debased, standard as to value," from late 14c. From c. 1200 of numbers or quantities, "large, great," of time or distance, "long;" good while "a considerable time" is from c. 1300; good way "a great distance" is mid-15c.

Why then, can one desire too much of a good thing. ["As You Like It"]

As good as "practically, virtually" is from mid-14c.; to be good for "beneficial to" is from late 14c. To make good "repay (costs, expenses), atone for (a sin or an offense)" is from late 14c. To have a good mind "have an earnest desire" (to do something) is from c. 1500. Good deed, good works were in Old English as "an act of piety;" good deed specifically as "act of service to others" was reinforced early 20c. by Boy Scouting. Good turn is from c. 1400. Good sport, of persons, is from 1906. The good book "the Bible" attested from 1801, originally in missionary literature describing the language of conversion efforts in American Indian tribes. Good to go is attested from 1989.

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