Online Etymology Dictionary

swarf (n.): "grit from a grinding tool," from Old English geswearf "filings," or Old Norse svarf "file dust," related to sverfa "to file."
swarm (n.): "cloud of bees or other insects," Old English swearm, from Proto-Germanic *swarmaz (cf. Old Saxon, Middle Low German swarm, Swedish svärm, Middle Dutch swerm, Old High German swarm, German Schwarm "swarm;" Old Norse svarmr "tumult"), usually derived from PIE imitative root *swer- (see susurration) on notion of humming sound. But OED suggests possible connection with base of swerve and ground sense of "agitated, confused, or deflected motion."
swarm (v.1): "to climb by clasping with the arms and legs alternately," 1540s, perhaps originally a sailors' word, of uncertain origin. Also recorded as swarve (16c.) and in Northern dialects swarble, swarmle.
swarm (v.2): "to leave a hive to start another," late 14c., from swarm (n.). Related: Swarmed; swarming.
swart (adj.): Old English sweart "black," from Proto-Germanic *swartaz (cf. Old Frisian and Middle Dutch swart, Old Norse svartr, German schwarz, Gothic swarts "dark-colored, black"), from PIE root *swordo- "dirty, dark, black" (source of sordid). The true Germanic word for "black," surviving in the Continental languages.
swarthy (adj.): 1580s, unexplained alteration of swarty (1570s), from swart + -y (2).
swash (n.): 1530s, "the fall of a heavy body or blow," possibly from wash with an intensifying s-. It also meant "pig-wash, filth, wet refuse" (1520s) and may have been imitative of the sound of water dashing against solid objects. The meaning "a body of splashing water" is first found 1670s; that of "a dashing or splashing" 1847.
swashbuckle (v.): 1897, back-formation from swashbuckling.
swashbuckler (n.): 1550s, "blustering, swaggering fighting man" (earlier simply swash, 1540s), from swash "fall of a blow" (see swash) + buckler "shield." The original sense seems to have been "one who makes menacing noises by striking his or an opponent's shield."
swashbuckling (adj.): 1690s, adjective formed from swashbuckler.
swastika (n.): Greek cross with arms bent at right angles, 1871 (later specifically as emblem of the Nazi party, 1932), from Sanskrit svastika-s, literally "being fortunate," from svasti-s "well-being, luck," from su- "well" + as-, root of asti "(he) is," from root of Latin esse "to be" (see essence). Also known as gammadion (Byzantine), cross cramponnee (heraldry), Thor's hammer, and, perhaps, fylfot. Originally an ancient cosmic or religious symbol thought to bring good luck. Use in reference to the Nazi emblem first recorded in English in 1932. The German word was Hakenkreuz, literally "hook-cross."
swat (v.): 1796, American English and northern England dialect word, possibly an alteration of Middle English swap "to strike, smite" (see swap), ultimately of imitative origin. Related: Swatted; swatting. The noun is recorded from 1800.
swatch (n.): 1510s, "the countercheck of a tally" (Northumberland dialect), later "a tally attached to cloth sent to be dyed" (1610s, in Yorkshire), of unknown origin. Meaning "a sample piece of cloth" is from 1640s.
swath (n.): Old English swæð, swaðu "track, trace, band," from Proto-Germanic *swathan, *swatho (cf. Old Frisian swethe "boundary made by a scythe," Middle Dutch swade, German Schwad "a row of cut grass"); ulterior connections uncertain. Meaning "space covered by the single cut of a scythe" emerged late 15c., and that of "strip, lengthwise extent" is from c.1600.
swathe (v.): Old English swaþian "to swathe," from swaðu "track, trace, band" (see swath). The noun meaning "infant's swaddling bands" was found in Old English as swaþum (dative plural).
swatter (n.): "instrument for swatting flies," 1917, agent noun from swat (v.).
sway (v.): c.1300, "to go, glide, move," probably from Old Norse sveigja "to bend, swing, give way," from Proto-Germanic *swaigijanan and related to swag (v.) and swing. The sense of "swing, wave, waver" is first recorded c.1500. Related: Swayed; swaying. The noun meaning "controlling influence" (to be under the sway of) is 1510s, from a transitive sense of the verb in Dutch and other languages. The verb in this sense is recorded in English from 1590s.
swear (v.): Old English swerian "take an oath" (class VI strong verb; past tense swor, past participle sworen), from Proto-Germanic *swarjanan, from root *swar- (cf. Old Saxon swerian, Old Norse sverja, Danish sverge, Old Frisian swera, Middle Dutch swaren, Old High German swerien, German schwören, Gothic swaren "to swear"), from PIE root *swer- "to speak, say" (cf. Old Church Slavonic svara "quarrel"). Also related to the second element in answer. The secondary sense of "use bad language" (early 15c.) developed from the notion of "invoke sacred names." Swear-word is American English colloquial from 1883. Swear off "desist as with a vow" is from 1898.
sweat (v.): Old English swætan "perspire, work hard," from the source of sweat (n.). Meaning "to be worried, vexed" is recorded from c.1400. Related: Sweated; sweating. Colloquial no sweat "no problem" attested from 1963.
sweat (n.): Old English swat "sweat," which became Middle English swote, but altered under the influence of the verb, from Proto-Germanic *swaita (cf. Old Saxon, Old Frisian swet, Old Norse sveiti, Danish sved "sweat," Swedish svett, Middle Dutch sweet, Dutch zweet, Old High German sweiz, German Schweiß), from PIE *sweid-/*swoid- (cf. Sanskrit svedah "sweat," Avestan xvaeda- "sweat," Greek hidros "sweat, perspiration," Latin sudor, Lettish swiedri, Welsh chwys "sweat"). Sweat equity is from 1968.
sweater (n.): "woolen vest or jersey, originally worn in rowing," 1882, from earlier sweaters "clothing worn to produce sweating and reduce weight" (1828), from sweat (v.). As a fashion garment, attested from 1925. Sweater girl is attested from 1940; Lana Turner (1920-1995) was the first, from her appearance in the film "They Won't Forget" (1937).
sweatpants (n.): by 1946, from sweat + pants.
sweatshirt (n.): by 1921, from sweat + shirt. Related: Sweatshirted.
sweatshop (n.): 1892, from sweat + shop (n.).
sweaty (adj.): late 14c., from sweat + -y (2). Related: Sweatiness.
Swede (n.): 1610s, from Low German, from Middle Low German Swede, back-formed from a source akin to Old English Sweoðeod, literally "Swede-people," from Sweon (plural) "Swedes" (Old Norse, Old Swedish Sviar), called by the Romans Suiones, probably from Proto-Germanic *sweba "free, independent," or else from *geswion "kinsman."
Sweden: c.1600, originally in Scottish (Swethin, Swadne, etc.), from Middle Dutch Sweden, probably a dative plural of Swede (earlier in English Sweden was used of the people and Swedeland of the country). In Old English, the country was Sweoland or Sweorice (cf. Old Norse sviariki, source of Swedish Sverige). Ultimately named for the original inhabitants (see Swede).
Swedenborgian: 1791, for Emanuel Svedberg, Swedish mystic and religious philosopher (1668-1772). His followers organized 1788 as The New Church.
Swedish (adj.): c.1600, from Swede + -ish. Related: Swedishness.
sweep (v.): c.1300, perhaps from a past tense form of Middle English swope "sweep," from Old English swapan "to sweep" (transitive & intransitive); see swoop. Related: Swept; sweeping.
sweep (n.): "range, extent," 1670s, from sweep (v.). In reference to police or military actions, it is attested from 1837. Sense of "a winning of all the tricks in a card game" is from 1814 (see sweepstakes); extended to other sports by 1960. As a shortened form of chimney-sweeper, first attested 1796.
sweepstakes (n.): "prize won in a race or contest," 1773, from Middle English swepestake "one who sweeps or wins all the stakes in a game" (late 15c., as the name of one of the King's ships), from swepen "sweep" (see sweep (v.)) + stake (n.2).
sweet (adj.): Old English swete "pleasing to the senses, mind or feelings," from Proto-Germanic *swotijaz (cf. Old Saxon swoti, Swedish söt, Danish sød, Middle Dutch soete, Dutch zoet, Old High German swuozi, German süß), from PIE root *swad- "sweet, pleasant" (Sanskrit svadus "sweet;" Greek hedys "sweet, pleasant, agreeable," hedone "pleasure;" Latin suavis "sweet," suadere "to advise," properly "to make something pleasant to").

To be sweet on someone is first recorded 1690s. Sweet-talk (v.) dates from 1935; earliest uses seem to refer to conversation between black and white in segregated U.S. Sweet sixteen first recorded 1767. Sweet dreams as a parting to one going to sleep is attested from 1898, short for sweet dreams to you, etc. Sweet and sour in cooking is from 1723 and not originally of oriental food.
sweet (n.): c.1300, "something sweet to the taste," also "beloved one," from sweet (adj.); the meaning "candy drop" is 1851 (earlier sweetie, 1721).
Sweet Adeline: "female barbershop singing group," 1947, from the name of a popular close harmony song by Armstrong & Gerard, "You're the Flower of my Heart, Sweet Adeline" (1903).
sweet tooth (n.): "fondness for sugary stuff," late 14c., from sweet (adj.) + tooth in the sense of "taste, liking" (see toothsome).
sweetbread (n.): "pancreas used as food" 1560s, from sweet (adj.); the -bread element may be from Old English bræd "flesh."
sweeten (v.): 1550s, from sweet (adj.) + verbal ending -en (1). The Middle English form of the verb was simply sweet, from Old English swetan. Related: Sweetened; sweetening.
sweetheart (n.): late 13c. as a form of address, 1570s as a synonym for "loved one;" from sweet (adj.) + heart. As an adjective, with reference to labor contracts, it is attested from 1959.
sweetie (n.): 1721, "lollipop;" 1778, "lover, sweetheart," from sweet (n.) + -ie.
swell (v.): Old English swellan "grow or make bigger" (past tense sweall, past participle swollen), from Proto-Germanic *swelnanan (cf. Old Saxon swellan, Old Norse svella, Old Frisian swella, Middle Dutch swellen, Dutch zwellen, Old High German swellan, German schwellen), of unknown origin.
swell (n.): early 13c., "a morbid swelling," from swell (v.). In reference to a rise of the sea, it is attested from c.1600. The meaning "wealthy, elegant person" is first recorded 1786; hence the adjectival meaning "fashionably dressed or equipped" (1810), both from the notion of "puffed-up, pompous" behavior. The sense of "good, excellent" first occurs 1897, and as a stand-alone expression of satisfaction it is recorded from 1930 in American English.
swelter (v.): c.1400, frequentative of swelten "be faint (especially with heat)," late 14c., from Old English sweltan "to die," from Proto-Germanic *swel- (cf. Old Saxon sweltan "to die," Old Norse svelta "to put to death, starve," Gothic sviltan "to die"), originally "to burn slowly," hence "to be overcome with heat or fever;" also the source of Old English swelan "to burn," from PIE root *swel- "to shine, burn" (see Selene). For specialization of words meaning "to die," cf. starve. Related: Sweltered; sweltering.
swerve (v.): early 13c., "to depart, make off;" early 14c., "to turn aside, deviate from a straight course," probably from Old English sweorfan "to rub, scour, file" (but sense development is difficult to trace), from Proto-Germanic *swerbanan (cf Old Norse sverfa "to scour, file," Old Saxon swebran "to wipe off"), from PIE root *swerbh-. Cognate words in other Germanic languages (cf. Old Frisian swerva "to creep," Middle Dutch swerven "to rove, stray") suggests the sense of "go off, turn aside" may have existed in Old English, though unrecorded. Related: Swerved; swerving.
swerve (n.): 1741, from swerve (v.).
swift (adj.): Old English swift "moving quickly," related to swifan "move in a course, sweep" (see swivel). Related: Swiftly; swiftness.
swift (n.): type of bird (several species of the family Cypselidæ, resembling swallows), 1660s, from swift (adj.) in reference to its swift flight. Regarded as a bird of ill-omen, if not downright demonic, probably for its shrill cry. The name earlier had been given to several small fast lizards (1520s).
swig (v.): 1650s, from swig (n.). Related: Swigged; swigging.
swig (n.): 1540s, "drink, liquor," later "big or hearty drink of liquor" (1620s), of unknown origin.
swill (n.): "liquid kitchen refuse fed to pigs," 1550s, from swill (v.).