sist Look up sist at Dictionary.com
legal term, from Latin sistere "to cause to stand" (see assist).
sister (n.) Look up sister at Dictionary.com
mid-13c., from Old English sweostor, swuster "sister," or a Scandinavian cognate (Old Norse systir, Swedish syster, Danish søster), in either case from Proto-Germanic *swestr- (cognates: Old Saxon swestar, Old Frisian swester, Middle Dutch suster, Dutch zuster, Old High German swester, German Schwester, Gothic swistar).

These are from PIE *swesor, one of the most persistent and unchanging PIE root words, recognizable in almost every modern Indo-European language (Sanskrit svasar-, Avestan shanhar-, Latin soror, Old Church Slavonic, Russian sestra, Lithuanian sesuo, Old Irish siur, Welsh chwaer, Greek eor). French soeur "a sister" (11c., instead of *sereur) is directly from Latin soror, a rare case of a borrowing from the nominative case.

According to Klein's sources, probably from PIE roots *swe- "one's own" + *ser- "woman." For vowel evolution, see bury. Used of nuns in Old English; of a woman in general from 1906; of a black woman from 1926; and in the sense of "fellow feminist" from 1912. Meaning "female fellow-Christian" is from mid-15c. Sister act "variety act by two or more sisters" is from vaudeville (1908).
sister-in-law (n.) Look up sister-in-law at Dictionary.com
mid-15c.; see sister + in-law.
sisterhood (n.) Look up sisterhood at Dictionary.com
"state of being a sister," late 14c., from sister + -hood. Meaning "a society of sisters" (usually a religious order) is from 1590s; sense of "women having some common characteristic or calling" is from c.1600.
sisterly (adj.) Look up sisterly at Dictionary.com
1560s, from sister + -ly (1). Related: Sisterliness.
Sistine (adj.) Look up Sistine at Dictionary.com
1769, literally "pertaining to Pope Sixtus," from Italian sistino, from Sixtus, name of five popes, from Latin sextus "sixth" (see Sextus). The "chapel" is named for Sixtus IV (Francesco della Rovere), pope 1471-84, who had it built. The painting by Raphael known as the Sistine Madonna is so called because it also shows Sixtus II, a 3c. martyr and saint; it is better known now for the two cherubs at the bottom of the picture who by 1900 were well-known in isolation from the rest of the picture in engravings, etc.
Sisyphean (adj.) Look up Sisyphean at Dictionary.com
"pertaining to or resembling the unceasingly recurring and fruitless labors of Sisyphus," 1630s, from Sisyphus + -an. Earlier Sisyphian (1590s).
Sisyphus Look up Sisyphus at Dictionary.com
King of Corinth, famed as "the craftiest of men," he was condemned in the afterlife to roll uphill a stone which perpetually rolls down again; Greek Sisyphos, a name of unknown origin. Liddell & Scott suggest a reduplication of syphos "the crafty" (with Aeolic -u- for -o-), but Klein calls this folk-etymology.
sit (v.) Look up sit at Dictionary.com
Old English sittan "to occupy a seat, be seated, sit down, seat oneself; remain, continue; settle, encamp, occupy; lie in wait; besiege" (class V strong verb; past tense sæt, past participle seten), from Proto-Germanic *setjan (cognates: Old Saxon sittian, Old Norse sitja, Danish sidde, Old Frisian sitta, Middle Dutch sitten, Dutch zitten, Old High German sizzan, German sitzen, Gothic sitan), from PIE root *sed- (1) "to sit" (see sedentary).

With past tense sat, formerly also set, now restricted to dialect, and sate, now archaic; and past participle sat, formerly sitten. In reference to a legislative assembly, from 1510s. Meaning "to baby-sit" is recorded from 1966.

To sit back "be inactive" is from 1943. To sit on one's hands was originally "to withhold applause" (1926); later, "to do nothing" (1959). To sit around "be idle, do nothing" is 1915, American English. To sit out "not take part" is from 1650s. Sitting pretty is from 1916.
sit-down (adj.) Look up sit-down at Dictionary.com
1836 of meals, 1936 of strikes, from verbal phrase (c.1200), from sit (v.) + down (adv.); as a noun, sit-down "act of sitting down" is from 1861.
sit-in Look up sit-in at Dictionary.com
1936, in reference to session musicians; 1937, in reference to union action; 1941, in reference to student protests. From the verbal phrase; see sit (v.) + in (adv.). To sit in is attested from 1868 in the sense "attend, be present;" from 1919 specifically as "attend as an observer."
sit-up (n.) Look up sit-up at Dictionary.com
also situp, kind of physical exercise, 1955, from the verbal phrase (attested from early 13c.); see sit (v.) + up (adv.). Related: Sit-ups.
sitar (n.) Look up sitar at Dictionary.com
1845, from Hindi sitar, from Persian sitar "three-stringed," from si "three" (Old Persian thri-; see three) + tar "string" (see tenet).
sitcom (n.) Look up sitcom at Dictionary.com
1964, from the first elements of situation comedy, a phrase attested from 1953 of television shows, 1943 of radio programs; see situation.
Even Bing Crosby has succumbed to series TV and will appear in a sitcom as an electrical engineer who happens to break into song once a week. ["Life," Sept. 18, 1964]
site (n.) Look up site at Dictionary.com
"place or position occupied by something," especially with reference to environment, late 14c., from Anglo-French site, Old French site "place, site; position," and directly from Latin situs "a place, position, situation, location, station; idleness, sloth, inactivity; forgetfulness; the effects of neglect," from past participle of sinere "let, leave alone, permit," from PIE *si-tu-, from root *tkei- "to settle, dwell, be home" (see home (n.)).
site (v.) Look up site at Dictionary.com
"to give a location to, place," 1590s, from site (n.). Related: Sited; siting.
sith (adv., conj., prep.) Look up sith at Dictionary.com
"since" (obsolete), Middle English, reduced from Old English siððan "then, thereupon; continuously, during which; seeing that," from *sið þon "subsequent to that," from sið "after," from Proto-Germanic *sith- "later, after" (cognates: Old Saxon sith "after that, since, later," German seit "since," Gothic seiþus "late"), from PIE *se- (2) "long, late" (see soiree).
sitophobia (n.) Look up sitophobia at Dictionary.com
"morbid aversion to food" (or certain foods), 1882, from Greek sitos "wheat, corn, meal; food," of unknown origin, + -phobia. Related: Sitophobe; sitophobic.
sitter (n.) Look up sitter at Dictionary.com
c.1300, "one that sits," agent noun from sit (v.). As short for baby-sitter from 1937.
sitting (n.) Look up sitting at Dictionary.com
early 13c., verbal noun from sit (v.). Meaning "a meeting of a body" is from c.1400. Meaning "interval during which one sits" (for some purpose, especially to have one's portrait taken) is from 1706. Sitting-room first recorded 1771. Slang sitting duck "easy target" first recorded 1944; literal sense is from 1867 (it is considered not sporting to shoot at one).
situ Look up situ at Dictionary.com
see in situ.
situate (v.) Look up situate at Dictionary.com
early 15c., "to place in a particular state or condition," from Medieval Latin situatus, past participle of situare "to place, locate," from Latin situs "a place, position" (see site). Related: Situated; situating.
situate (adj.) Look up situate at Dictionary.com
1520s, now obsolete, adjective from Late Latin situatus, past participle of situare (see situate (v.)).
situation (n.) Look up situation at Dictionary.com
early 15c., "place, position, or location," from Middle French situation or directly from Medieval Latin situationem (nominative situatio) "a position, situation," noun of action from past participle stem of situare "to place, locate" (see situate). Meaning "state of affairs" is from 1710; meaning "employment post" is from 1803.
situational (adj.) Look up situational at Dictionary.com
1903, from situation + -al. Related: Situationally. Situational ethics attested from 1969 (situation ethics first attested 1955).
situs (n.) Look up situs at Dictionary.com
Latin, "situation, position" (see site). In technical uses in English, "proper or original position and location of something" (as in in situ).
sitz-bath (n.) Look up sitz-bath at Dictionary.com
1849, a hybrid, from German Sitzbad, literally "bath in a sitting position," with English bath for German Bad.
sitzkrieg (n.) Look up sitzkrieg at Dictionary.com
1940, "static warfare" (such as prevailed in Europe in the winter of 1939-40), R.A.F. coinage on analogy of blitzkrieg (q.v.), from German sitz "a sitting."
Siva (n.) Look up Siva at Dictionary.com
also Shiva, one of the three supreme gods of Hinduism, lord of destruction and reproduction, 1788, from Hindi Shiva, from Sanskrit Sivah, literally "propitious, gracious," from PIE *ki-wo-, from root *kei- "beloved, dear" (connected with Latin civis "citizen," literally "member of a household"), also "to lie, couch" (compare cemetery). But by some this is said to be a euphemism. Related: Sivaism; Sivaistic.
six (n.) Look up six at Dictionary.com
Old English siex, six, sex, from Proto-Germanic *sekhs (cognates: Old Saxon and Danish seks, Old Norse, Swedish, and Old Frisian sex, Middle Dutch sesse, Dutch zes, Old High German sehs, German sechs, Gothic saihs), from PIE *s(w)eks (cognates: Sanskrit sas, Avestan kshvash, Persian shash, Greek hex, Latin sex, Old Church Slavonic sesti, Polish sześć, Russian shesti, Lithuanian szeszi, Old Irish se, Welsh chwech).

Six-shooter, usually a revolver with six chambers, is first attested 1844; six-pack of beverage containers is from 1952, of abdominal muscles by 1995. Six of one and half-a-dozen of the other "little difference" is recorded from 1833. Six-figure in reference to hundreds of thousands (of dollars, etc.) is from 1840. Six feet under "dead" is from 1942.

Phrase at sixes and sevens originally was "hazarding all one's chances," first in Chaucer, perhaps from dicing (the original form was on six and seven); it could be a corruption of on cinque and sice, using the French names (which were common in Middle English) for the highest numbers on the dice. Meaning "at odds, in disagreement or confusion" is from 1785, perhaps via a notion of "left unsettled."
sixfold (adj.) Look up sixfold at Dictionary.com
Old English sixfeald; see six + -fold. Similar formation in Danish sexfold, Dutch zes-voudig; German sechsfältig, Swedish sexfaldig.
sixpence (n.) Look up sixpence at Dictionary.com
late 14c., "sum of six pennies," from six + pence. As a specific British coin, from 1590s. Sixpenny (adj.) had a figurative sense "paltry, cheap, petty, worthless" by 1560s; sixpenny nails (early 15c.) cost so much per hundred.
sixteen Look up sixteen at Dictionary.com
Old English sixtyne, from siex (see six) + -teen. Similar formation in Old Frisian sextine, Middle Dutch sestien, Dutch zestien, German sechszehn, Old Norse sextan.
The age of the gods is always sixteen. Sixteen represents the number of perfection, of plenitude. In man it is after the sixteenth year that the first elements of decay begin to appear, and when the moon reaches the sixteenth digit it begins to decrease. [Alain Daniélou, "The Myths and Gods of India"]
From Latin contracted form sexdecim, sedecim come Italian sedici, French seize.
sixteenmo (n.) Look up sixteenmo at Dictionary.com
"book printed on sheets of 16 leaves," 1847, from an English reading of the printers' Latin abbreviation 16-mo, representing sexto decimo "sixteen."
sixteenth (adj.) Look up sixteenth at Dictionary.com
early 13c., from sixteen + -th (1); replacing sixtethe, sixteothe, forms based on Old English syxteoða. Cf Old Frisian sextinda, Middle Dutch sestiende, German sechzehnte, Old Norse sextandi. Musical sixteenth note is from 1861.
sixth (adj.) Look up sixth at Dictionary.com
1520s, replacing Middle English sixte (c.1200), from Old English syxte, from siex (see six). Compare Old Frisian sexta, Middle Dutch seste, Old High German sehsto, German sechste, Gothic saihsta. With ending conformed to -th (1). Related: Sixthly. The noun meaning "a sixth part" is from 1550s. As a music tone, from 1590s. Sixth sense "supernatural perception of objects" is attested from 1712; earlier it meant "titillation, the sense that apprehends sexual pleasure" (1690s, from Scaliger).
Then said Peter, That is false; for there is a sixth Sense, that of Prescience : for the other five Senses are capable only of Knowledg ; but the Sixth of Foreknowledg ; which Sense the Prophets had. [William Whitson, "Primitive Christianity Reviv'd," vol. V, London, 1712]
sixties (n.) Look up sixties at Dictionary.com
1848 as the years of someone's life between 60 and 69; 1827 as the seventh decade of years in a given century. See sixty.
sixtieth Look up sixtieth at Dictionary.com
Old English sixteogoða "sixtieth;" see sixty + -th (1).
sixty Look up sixty at Dictionary.com
Old English sixtig, from siex (see six) + -tig (see -ty (1)). Similar formation in Old Norse sextugr, sextögr, sextigir, Old Frisian sextich, Middle Dutch sestig, Dutch zestig, Old High German sehszug, German sechzig. Phrase sixty-four dollar question is 1942, from radio quiz show where that was the top prize.
sixty-nine (n.) Look up sixty-nine at Dictionary.com
in sexual sense, 1888, as a translation of French faire soixante neuf, literally "to do 69." So called from the similarity of positions to the arrangement of the numerals.
sixtyfold Look up sixtyfold at Dictionary.com
also sixty-fold, Old English sixtigfeald; see sixty + -fold.
sizar (n.) Look up sizar at Dictionary.com
also sizer, at certain British universities, a student of limited means who received school meals for free, 1580s, from size (n.) in a specialized sense "ration, allowance for provisions."
size (n.) Look up size at Dictionary.com
c.1300, "an ordinance to fix the amount of a payment or tax," from Old French sise, shortened form of assise "session, assessment, regulation, manner" (see assize), probably a misdivision of l'assise as la sise. The sense of "extent, amount, volume, magnitude" (c.1300) is from the notion of regulating something by fixing the amount of it (weights, food portions, etc.). Specific sense of "set of dimensions of a manufactured article for sale" is attested from 1590s.
size (v.) Look up size at Dictionary.com
c.1400, "to regulate," from size (n.). Meaning "to make of a certain size" is from c.1600; that of "to classify according to size" is first attested 1630s. Verbal phrase size up "estimate, assess" is from 1847 and retains the root sense of size (n.). Related: Sized; sizing.
sizeable (adj.) Look up sizeable at Dictionary.com
also sizable, 1610s, "of relatively good, suitable, or desirable size, usually somewhat large" [Century Dictionary], from size + -able. Related: Sizeably; sizeableness.
sizer (n.) Look up sizer at Dictionary.com
"device for measuring sizes," 1670s, agent noun from size (v.).
sizzle (v.) Look up sizzle at Dictionary.com
c.1600, "to burn with a hissing sound," perhaps a frequentative form of Middle English sissen "hiss, buzz" (c.1300), of imitative origin. The figurative sense is attested from 1859. Related: Sizzled; sizzling. The noun is first recorded 1823.
ska (n.) Look up ska at Dictionary.com
1964, Jamaican, of unknown origin.
skag (n.) Look up skag at Dictionary.com
"heroin," 1967, American English, earlier "cigarette" (1915), of unknown origin.
skald (n.) Look up skald at Dictionary.com
"Scandinavian poet and singer of medieval times," 1763, from Old Norse skald "skald, poet" (9c.), of unknown origin, perhaps from PIE root *sekw- (3) "to say, utter." The modern word is an antiquarian revival. "Usually applied to Norwegian and Icelandic poets of the Viking period and down to c 1250, but often without any clear idea as to their function and the character of their work" [OED]. Related: Scaldic.