Online Etymology Dictionary

seven-year itch (n.): 1899, American English, some sort of skin condition (sometimes identified with poison ivy infection) that either lasts seven years or returns every seven years. Jocular use for "urge to stray from marital fidelity" is attested from 1952, as the title of the Broadway play (made into a film, 1955) by George Axelrod (1922-2003), in which the lead male character reads an article describing the high number of men have extra-marital affairs after seven years of marriage.
seventeen: Old English seofontyne; see seven + -teen.
seventh: Old English seofunda (Anglian), from Proto-Germanic *sebundon (cf. Old Norse sjaundi, Old High German sibunto), from seven (q.v.).
seventies: 1859 as the years of someone's life between 70 and 79; 1837 as a decade of years in a given century. See seventy.
seventy: Old English (hund)seofontig, from seofon (see seven) + -tig (see -ty (1)). Cf. Old Frisian soventich, Middle Dutch seventich, Old Norse sjau tiger.
sever (v.): c.1300, from Anglo-French severer, Old French sevrer "to separate," from Vulgar Latin *seperare, from Latin separare "to separate" (see separate).
several (adj.): early 15c., "existing apart," from Anglo-French several, from Middle French seperalis "separate," from Latin separe (ablative of *separ "distinct"), back-formation from separare "to separate" (see separate). Meaning "various, diverse, different" is attested from c.1500; that of "more than one" is from 1530s, originally in legal use.
severally (adv.): "separately," late 14c., from several + -ly (2).
severance (n.): early 15c., from Anglo-French, from Old French sevrance, from sevrer (see sever). Meaning "discharge from employment contract" is attested from 1941. Severance pay attested by 1942.
severe (adj.): 1540s, from French sévère, from Latin severus (see severity).
severely (adv.): 1540s, from severe + -ly (2).
severity (n.): late 15c., "austerity or strictness of life," from Middle French severite, from Latin severitas, from severus "stern, strict, serious," possibly from *se vero "without kindness," from se "without" (see secret) + *vero "kindness," neuter ablative of verus "true" (see very). Meaning "strictness in dealing with others" is recorded from 1520s.
sew (v.): Old English siwian "to stitch," earlier siowian, from Proto-Germanic *siwjanan (cf. Old Norse syja, Swedish sy, Old High German siuwan, Gothic siujan "to sew"), from PIE root *syu- "to bind, sew" (cf. Sanskrit sivyati "sews," sutram "thread, string;" Greek hymen "thin skin, membrane," hymnos "song;" Latin suere "to sew, sew together;" Old Church Slavonic sijo "to sew," sivu "seam;" Lettish siuviu, siuti "to sew," siuvikis "tailor;" Russian svec "tailor"). Related: Sewed; sewing. Sewing machine is attested from 1847.
sewage (n.): 1834, from sew (v.) "to drain, draw off water" (late 15c., from sewer) + -age.
sewer (n.): "conduit," c.1400, from Anglo-French sewere, Old North French sewiere "sluice from a pond" (13c.), literally "something that makes water flow," from shortened form of Gallo-Romance *exaquaria (cf. Middle French esseveur), from Latin ex- "out" + aquaria, fem. of aquarius "pertaining to water," from aqua "water."
sex (n.): late 14c., "males or females collectively," from Latin sexus "state of being either male or female, gender." "Commonly taken with seco as division or 'half' of the race" [Tucker], which would connect it to secare "to divide or cut" (see section). Meaning "quality of being male or female" first recorded 1520s. Meaning "sexual intercourse" first attested 1929 (in writings of D.H. Lawrence); meaning "genitalia" is attested from 1938. Sex appeal attested by 1904.
For the raw sex appeal of the burlesque "shows" there is no defense, either. These "shows" should be under official supervision, at the least, and boys beneath the age of eighteen forbidden, perhaps, to attend their performance, just as we forbid the sale of liquors to minors. [Walter Prichard Eaton, "At the New Theatre and Others: The American Stage, Its Problems and Performances," Boston, 1910]
Sex drive is from 1918; sex object is 1901; sex symbol is 1871 in anthropology; the first person to whom it was applied seems to have been Marilyn Monroe (1959).
sex (v.): 1884, "to determine the sex of," from sex (n.); to sex (something) up "increase the sex appeal of" is recorded from 1942. Related: Sexed; sexing.
sexagenarian (n.): 1738, "person sixty years old," from Latin sexagenarius "containing sixty," from sexagenarius, from sexageni "sixty each," from sex (see six) + -genaria "ten times," from PIE *dkm-ta-, from *dekm- "ten" (see ten).
sexiness (n.): 1922, from sexy + -ness.
sexism (n.): 1968; see sexist + -ism.
sexist (adj.): 1965, on model of racist, coined by Pauline M. Leet, director of special programs at Franklin & Marshall College, Lancaster, Pennsylvania, U.S., in a speech which was circulated in mimeograph among feminists. Popularized by use in print in Caroline Bird's introduction to "Born Female" (1968).
sexpert (n.): "sex therapist," 1924, from jocular merger of sex + expert.
sexploitation (n.): 1942, from sex + exploitation.
sexpot (n.): "erotically willing and desirable female," 1929, from sex + pot, perhaps suggested by fleshpot.
sext (v.): by 2005, from contraction of sex + text (v.). Related: Sexted; sexting.
sext (n.): early 15c., from Latin sexta (hora), fem. of sextus, ordinal of sex (see six).
sextant (n.): instrument for determining latitude, 1620s, from Modern Latin sextans, said to have been coined c.1600 by Danish astronomer Tycho Brahe, from Latin sextans "a sixth," from sex "six" (see six). So called because the sextans has a graduated arc equal to a sixth part of a circle.
sextet (n.): 1841, altered (by influence of German Sextett) from sestet (1801), from Italian sestetto, diminutive of sesto "sixth," from Latin sextus (see Sextus).
sextile: 1550s (adj.); 1590s (n.); from Latin sextilis, from sextus "sixth" (see Sextus).
sexton (n.): c.1300, sekesteyn, "person in charge of the sacred objects of a church," from Old French segrestien, from Medieval Latin sacristanus (see sacristan). Sense of "custodian of a church" first recorded 1580s.
sextuplet: 1852, from adjective sextuple (1620s), from Latin sextus "sixth," from sex "six" (see six). Patterned on triplet, etc.
Sextus: masc. proper name, from Latin, properly "the sixth," originally denoting a sixth child, from sextus "sixth," from sex "six" (see six; also see Octavian).
sexual (adj.): 1650s, "of or pertaining to the fact of being male or female," from Late Latin sexualis "relating to sex," from Latin sexus (see sex). Meaning "pertaining to copulation or generation" is from 1766; sexual intercourse attested by 1778; sexual orientation by 1967; sexual harassment by 1975. Sexual revolution attested by 1962.
sexuality (n.): 1800, "action of being sexual;" see sexual + -ity. Meaning "capability of sexual feelings" is from 1879. Meaning "sexual identity" is by 1980.
sexualization (n.): 1889, noun of action from sexualize.
sexualize (v.): 1839, from sexual + -ize. Related: Sexualized; sexualizing.
sexy (adj.): 1905, from sex + -y (2). Originally "engrossed in sex;" sense of "sexually attractive" is 1923, first in reference to Valentino. An earlier word in this sense was sexful (1898). Related: Sexier; sexiest.
Seychelles: renamed 1756 in honor of French finance minister Jean Moreau de Séchelles; spelling altered 1794 by the English when they took the islands from France.
sforzando: 1801, from Italian sforzando, gerundive of sforza "to force."
sfumato: 1847, from Italian sfumato, literally "smoked."
sh: exclamation used to urge or request silence, 1847. The gesture of putting a finger to the lips to express silence is attested from Roman times.
sh-: sound represented in Old English by -sc- (e.g. fisc "fish"), which originally was pronounced "-sk-" but which by late Old English had softened to "-sh-." Modern words with -sc- mostly are foreign (generally Scandinavian) imports.

The "sh" sound did not exist in Old French, therefore French scribes after the Norman conquest often represented it with -ssh- in medial and final positions, and sch- in initial positions. The spelling -sh- has been standard since Caxton, and probably is a worn-down form of Middle English -sch-.

In some East Anglian texts from 14c.-15c., x- is used (e.g. xal, xulde for shall, should), which would have given the language a very different look had it prevailed, but the London-based sh- ended up as the standard form.
Shabbat (n.): from Hebrew shabbat (see Sabbath).
shabby (adj.): 1660s, from shab "scab" (now only dialectal, in reference to a disease of sheep), from Old English sceabb (see scab) + -y (2). With sound change as described in sh-. Cf. Middle Dutch schabbich, German schäbig "shabby." Related: Shabbily; shabbiness. Shabby-genteel "run-down but trying to keep up appearances" first recorded 1754.
shack (n.): 1878, American English and Canadian English, of unknown origin, perhaps from Mexican Spanish jacal, from Nahuatl xacalli "wooden hut." Or perhaps a back-formation from dialectal English shackly "shaky, rickety" (1843), a derivative of shack, a dialectal variant of shake (v.). Another theory derives shack from ramshackle. Slang verb phrase shack up "cohabit" first recorded 1935 (in Zora Neale Hurston).
shackle (n.): Old English sceacel, from Proto-Germanic *skakula- (cf. Middle Dutch, Dutch schakel "link of a chain," Old Norse skökull "pole of a carriage"), of uncertain origin. The common notion of "something to fasten or attach" makes a connection with shake unlikely.
shackle (v.): mid-15c., from shackle (n.). Related: Shackled; shackling.
shacklebolt (n.): "bolt which passes through the eyes of a shackle," 1680s, from shackle (n.) + bolt (n.).
shad (n.): Old English sceadd, possibly from Scandinavian (cf. Norwegian dialectal skadd "small whitefish"); but cf. Welsh ysgadan (plural), Irish and Gaelic sgadan "herring." Low German schade may be from English.
shade (n.): Old English sceadu "shade, shadow, darkness," also "shady place, protection from glare or heat," from Proto-Germanic *skadwo (cf. Old Saxon skado, Middle Dutch scade, Dutch schaduw, Old High German scato, German Schatten, Gothic skadus), from PIE *skotwa, from root *skot- "dark, shade" (cf. Greek skotos "darkness," Albanian kot "darkness," Old Irish scath, Old Welsh scod, Breton squeut "darkness"). Meaning "grade of color" first recorded 1680s (cf. French nuance, from nue "cloud"). Meaning "ghost" is from 1610s. Sense of "window blind" first recorded 1867, American English.