Online Etymology Dictionary

slot (n.1): late 14c., "hollow at the base of the throat above the breastbone," from Old French esclot "hoofprint of a deer or horse," of uncertain origin, probably from Old Norse sloð "trail" (see sleuth). Original sense is rare or obsolete in Modern English; sense of "narrow opening into which something else can be fitted" is first recorded 1520s. Meaning "middle of the (semi-circular) copy desk at a newspaper," the spot occupied by the chief sub-editor, is recorded from 1917. The sense of "opening in a machine for a coin to be inserted" is from 1888 (slot machine first attested 1891). The sense of "position in a list" is first recorded 1942; verb sense of "designate, appoint" is from 1960s. Slot car first attested 1966.
slot (v.2): 1560s, "to bolt a door," from slot (n.2). Related: Slotted; slotting.
slot (v.1): 1747, "provide with a slot, cut slots in," from slot (n.1). Meaning "drop a coin in a slot" is from 1888. Sense of "take a position in a slot" is from 1940; that of "fit (something) into a slot" is from 1966. Oldest sense is obsolete: "stab in the base of the throat" (c. 1400). Related: Slotted; slotting.
sloth (n.): late 12c., "indolence, sluggishness," formed from Middle English slou, slowe (see slow (adj.)) + abstract formative -th (2). Replaced Old English slæwð "sloth, indolence." Sense of "slowness, tardiness" is from mid-14c. As one of the deadly sins, it translates Latin accidia.

The slow-moving mammal first so called 1610s, a translation of Portuguese preguiça "slowness, slothfulness," from Latin pigritia "laziness" (compare Spanish perezosa "slothful," also "the sloth").
slothful (adj.): c. 1400, from sloth + -ful. Related: Slothfully; slothfulness. For the latter, Middle English also had sloth-head (c. 1300), with Middle English -hede, cognate with -hood.
slouch (n.): 1510s, "lazy man," variant of slouk (1560s), probably from a Scandinavian source, perhaps Old Norse slokr "lazy fellow," and related to slack (adj.) on the notion of "sagging, drooping." Meaning "stooping of the head and shoulders" first recorded 1725. Slouch hat, made of soft material, first attested 1764.
slouch (v.): "walk with a slouch," 1754; "have a downcast or stooped aspect," 1755; from slouch (n.). Related: Slouched; slouching (1610s as a past participle adjective; 1660s of persons, 1690s of hats).
slouchy (adj.): 1690s, from slouch + -y (2). Related: Slouchily; slouchiness.
slough (n.1): "muddy place," Old English sloh "soft, muddy ground," of uncertain origin. Compare Middle Low German sloch "muddy place," Middle High German sluoche "ditch." Figurative use (of moral sunkenness or Bunyan's "Slough of Despond," 1678) attested from mid-13c.
slough (v.): "to cast off" (as the skin of a snake or other animal), 1720, originally of diseased tissue, from Middle English noun slough "shed skin of a snake" (see slough (n.)). Related: Sloughed; sloughing.
slough (n.2): "cast-off skin" (of a snake or other animal), early 14c., slughe, slouh, probably related to Old Saxon sluk "skin of a snake," Middle High German sluch "snakeskin, wineskin," Middle Low German slu "husk, peel, skin," German Schlauch "wineskin;" from Proto-Germanic *sluk-, of uncertain origin, perhaps from PIE root *sleug- "to glide."
Slovak: 1829 (n.), 1887 (adj.), from French Slovak, from the people's own name (compare Slovak and Czech Slovak, plural Slovaci; Polish Słowak; Russian Slovak; German Slowake). Related: Slovakian.
sloven (n.): late 15c., "immoral woman," later (16c.) also "rascal, knave" (regardless of gender); probably from a continental Germanic source, compare Middle Flemish sloovin "a scold," sloef "untidy, shabby," Dutch slof "careless, negligent," Middle Low German sloven "put on clothes carelessly," from Proto-Germanic *slaubjan, from PIE *sleubh- "to slide, slip" (see sleeve). Meaning "person careless of dress or negligent of cleanliness" is from 1520s. Also see slut.
Slovene (n.): Slavic people of Carinthia and Styria, 1883, from German Slowene, from Slovenec, the people's own name, originally literally "Slav." A survival of the old native designation of the Slavic people, compare Old Church Slavonic Slovene. Related: Slovenian.
slovenly (adj.): 1510s, "low, base, lewd," later "untidy, dirty" (1560s), from sloven + -ly (1). Related: Slovenliness; also in this sense was slovenry (1540s), which OED reports in common use early 17c.
slow (adj.): Old English slaw "inactive, sluggish, torpid, lazy," also "not clever," from Proto-Germanic *slæwaz (source also of Old Saxon sleu "blunt, dull," Middle Dutch slee, Dutch sleeuw "sour, tart, blunt," Old High German sleo "blunt, dull," Old Norse sljor, Danish sløv, Swedish slö "blunt, dull"). Meaning "taking a long time" is attested from early 13c. Meaning "dull, tedious" is from 1841. As an adverb c. 1500. The slows "imaginary disease to account for lethargy" is from 1843.
slow (v.): 1550s, "make slower;" 1590s, "go slower," from slow (adj.). Related: Slowed; slowing. Old English had slawian (intransitive) "to be or become slow, be sluggish," but the modern use appears to be a 16c. re-formation.
slowdown (n.): also slow-down, 1892, "act of going more slowly," from verbal phrase; see slow (v.) + down (adv.).
slowly (adv.): Old English slawlice "slowly, sluggishly;" see slow (adj.) + -ly (2).
slowness (n.): c. 1300, from slow (adj.) + -ness.
slowpoke (n.): also slow poke, 1848, American English from slow (adj.) + poke (n.3), the name of a device, like a yoke with a pole, attached to domestic animals such as pigs and sheep to keep them from escaping enclosures. Bartlett (1859) calls it "a woman's word."
slubberdegullion (n.): "a slobbering or dirty fellow, a worthless sloven," 1610s, from slubber "to daub, smear; behave carelessly or negligently" (1520s), probably from Dutch or Low German (compare slobber (v.)). Second element appears to be an attempt to imitate French; or perhaps it is French, related to Old French goalon "a sloven." Century Dictionary speculates the -de- means "insignificant" or else is from hobbledehoy.
sludge (n.): "mud, mire, ooze," 1640s, of uncertain origin, possibly a variant of Middle English slutch "mud, mire," or a variant of slush (n.).
sluff (v.): "avoid work," 1951 slang variant of slough (v.).
slug (n.1): "shell-less land snail," 1704, originally "lazy person" (early 15c.); related to sluggard.
slug (n.2): "lead bit," 1620s, perhaps a special use of slug (n.1), perhaps on some supposed resemblance. Meaning "token or counterfeit coin" first recorded 1881; meaning "strong drink" first recorded 1756, perhaps from slang fire a slug "take a drink," though it also may be related to Irish slog "swallow." Journalism sense is from 1925, originally a short guideline for copy editors at the head of a story.
slug (n.3): "a hard blow," 1830, dialectal, of uncertain origin; perhaps related to slaughter or perhaps a secondary form of slay.
slug (v.): "deliver a hard blow with the fist," 1862, from slug (n.3). Related: Slugged; slugging. Slugging-match is from 1878.
slug-a-bed (n.): also slugabed, 1590s, with bed (n.) + obsolete verb slug "be lazy, intert" (early 15c.), which is perhaps from Scandinavian (see sluggard).
slugfest (n.): 1910, originally in reference to baseball, from slug (n.3) + -fest.
sluggard (n.): late 14c., late 13c. as a surname, "habitually lazy person," from Middle English sluggi "sluggish, indolent," probably from a Scandinavian word such as dialectal Norwegian slugga "be sluggish," dialectal Norwegian sluggje "heavy, slow person," dialectal Swedish slogga "to be slow or sluggish." Adjective sluggy is attested in English from early 13c.
'Tis the voice of a sluggard -- I heard him complain:
"You have wak'd me too soon, I must slumber again."
[Isaac Watts, 1674-1748]

'Tis the voice of the Lobster: I heard him declare
"You have baked me too brown, I must sugar my hair."
["Lewis Carroll" (Charles L. Dodgson), 1832-1898]
As an adjective meaning "sluggish, lazy" from 1590s. Related: Sluggardly.
slugger (n.): 1877, originally in baseball, agent noun from slug (v.). Meaning "one who hits with the fists" is from 1883.
sluggish (adj.): mid-15c., from Middle English slugge "lazy person" (see sluggard) + -ish. Earlier adjective was sluggi (early 13c.). Related: Sluggishly; sluggishness.
sluice (n.): c. 1400, earlier scluse (mid-14c.), a shortening of Old French escluse "sluice, floodgate" (Modern French écluse), from Late Latin exclusa "barrier to shut out water" (in aqua exclusa "water shut out," i.e. separated from the river), from fem. singular of Latin exclusus, past participle of excludere "to shut out" (see exclude).
sluice (v.): 1590s, from sluice (n.). Related: Sluiced; sluicing.
slum (n.): 1845, from back slum "dirty back alley of a city, street of poor or low people" (1825), originally a slang or cant word meaning "room," especially "back room" (1812), of unknown origin, pastime popularized by East End novels. Related: slums. Slumscape is from 1947.
slum (v.): "visit slums of a city," especially for diversion or amusement, often under guise of philanthropy, 1884, from slum (n.). Pastime popularized by East End novels. Earlier it meant to visit slums for disreputable purposes or in search of vice (1860). Related: Slumming.
slumber (v.): mid-14c. alteration of slumeren (mid-13c.), frequentative form of slumen "to doze," probably from Old English sluma "light sleep" (compare Middle Dutch slumen, Dutch sluimeren, German schlummern "to slumber"). Frequentative on the notion of "intermittent light sleep." For the -b-, compare number, lumber, chamber, etc. Related: Slumbered; slumbering.
slumber (n.): mid-14c., from slumber (v.). Slumber party first recorded 1942. Slumberland is from 1875.
slumlord (n.): also slum-lord, 1899, from slum landlord (1885); see slum (n.) + landlord.
slummy (adj.): 1873, from slum (n.) + -y (2). Related: Slummily; slumminess.
slump (v.): 1670s, "fall or sink into a muddy place," probably from a Scandinavian source such as Norwegian and Danish slumpe "fall upon," Swedish slumpa; perhaps ultimately of imitative origin. Related: Slumped; slumping.
The word "slump," or "slumped," has too coarse a sound to be used by a lady. [Eliza Leslie, "Miss Leslie's Behaviour Book," Philadelphia, 1839]
Economic sense from 1888.
slump (n.): "act of slumping, slumping movement," 1850; "heavy decline in prices on the stock exchange," 1888, from slump (v.). Generalized by 1922 to "sharp decline in trade or business."
slung: past tense and past participle of sling.
slunk: past tense and past participle of slink (v.).
slur (n.): "deliberate slight, disparaging or slighting remark," c. 1600, from dialectal slur "thin or fluid mud," from Middle English slore (mid-15c.), cognate with Middle Low German sluren, Middle Dutch sloren "to trail in mud." Related to East Frisian sluren "to go about carelessly," Norwegian slora "to be careless." Literal sense of "a mark, stain, smear" is from 1660s in English. The musical sense (1746) is from the notion of "sliding." Meaning "act or habit of slurring" in speech is from 1882.
slur (v.): c. 1600, "smear, soil by smearing," from slur (n.). Meaning "disparage depreciate" is from 1650s. In music, from 1746; of speech, from 1893. Related: Slurred; slurring.
slurp (v.): 1640s, from Dutch slurpen, perhaps of imitative origin (compare German schlürfen). Related: Slurped; slurping. The noun is first recorded 1949, from the verb.
slurry (n.): mid-15c., "mud, slime, semi-fluid mix of water and dirt or clay," probably related to Middle English sloor "thin or fluid mud" (see slur (n.)).
slush (n.): 1640s, "melting snow, snow and water," perhaps from a Scandinavian source (compare Norwegian and Swedish slask "slushy ground;" obsolete Danish slus "sleet"), all probably imitative of the sound of sloshing. Slush fund is first attested 1839, from an earlier sense of slush "refuse fat" (1756); the money from the sale of a ship's slush was distributed among the officers, which was the original sense of the phrase. The extended meaning "money collected for bribes and to buy influence" is first recorded 1874, no doubt with suggestions of "greasing" palms.