Online Etymology Dictionary

slippage (n.): 1850, from slip (v.) + -age.
slipper (n.): type of footwear, late 15c., agent noun from slip (v.), the notion being of a shoe that is "slipped" onto the foot.
slippery (adj.): "having a slippery surface," c.1500, from Middle English sliper (adj.), from Old English slipor "slippery" (see slip (v.)) + -y (2). Metaphoric sense of "deceitful" is first recorded 1550s. Related: Slipperiness. In a figurative sense, slippery slope is first attested 1844.
slipshod (adj.): 1570s, "wearing slippers or loose shoes," from slip (v.) + shod "wearing shoes." Sense of "slovenly, careless" is from 1815.
slipstream (n.): also slip-stream, 1913, from slip + stream (n.).
slit (v.): Old English slitan "cut or tear up, slit," from Proto-Germanic *slitanan (cf. Old Saxon slitan, Old Norse slita, Middle Low German, Middle Dutch sliten, Dutch slijten, Old High German slizan, German schleißen "to slit"). Slit skirt is attested from 1913.
slit (n.): mid-13c., from slit (v.). Slang sense of "vulva" is attested from 1640s.
slither (v.): Old English slidrian "to slide on a loose slope," a frequentative form of slidan "to slide" (see slide). Meaning "to walk in a sliding manner" is attested from 1848. In reference to reptile motion, attested from 1839. Related: Slithered; slithering.
sliver (n.): late 14c., from obsolete verb sliven "to split, cleave," from Old English toslifan "to split, cleave," from Proto-Germanic *slifanan.
Sloane Ranger (n.): "fashionable but conventional young woman of London," 1975, from Sloane Square, near Chelsea, with a play on Lone Ranger.
slob (n.): 1780, "mud, muddy land," from Irish slab "mud," itself probably borrowed from English slab "muddy place" (c.1600), from a Scandinavian source (cf. Icelandic slabb "sludge"). The meaning "untidy person" is first recorded 1861.
slobber (v.): c.1400, probably related to Frisian slobberje "to slurp," Middle Low German slubberen "slurp," Middle Dutch overslubberen "wade through a ditch," etc., all of imitative origin. Related: Slobbered; slobbering.
sloe (n.): "fruit of the blackthorn," Old English slah (plural slan), from Proto-Germanic *slaikhwon (cf. Middle Dutch, Dutch slee, Old High German sleha, German Schlehe), from PIE *sleie- "blue, bluish, blue-black" (see livid). Sloe-eyed is attested from 1867; sloe gin first recorded 1895.
slog (v.): 1824, "hit hard," probably variant of slug (v.3) "to strike." Sense of "walk doggedly" first recorded 1872. Related: Slogged; slogging. Noun sense of "hard work" is from 1888.
slogan (n.): 1510s, "battle cry," from Gaelic sluagh-ghairm "battle cry used by Scottish Highland or Irish clans," from sluagh "army, host, slew" + gairm "a cry" (see garrulous). Metaphoric sense of "distinctive word or phrase used by a political or other group" is first attested 1704. Sloganeering is attested from 1941.
sloop (n.): 1620s, from Dutch sloep "a sloop," probably from French chaloupe, from Old French chalupe "small, sloop-rigged vessel," perhaps related to English shallop. In military use, a small ship of war carrying guns on the upper deck only.
slop (n.): c.1400, "mudhole," probably from Old English -sloppe "dung" (in cusloppe "cow dung"), related to slyppe "slime" (see slip (v.)). Meaning "semiliquid food" first recorded 1650s; that of "refuse liquid of any kind" (usually slops) is from 1815.
slop (v.): "to spill carelessly," 1550s, from slop (n.). Related: Slopped; slopping.
slope (n.): 1610s, from slope (v.). Derogatory slang meaning "Oriental person" is attested from 1948.
slope (v.): 1590s, from earlier adjective meaning "slanting" (c.1500), probably from Middle English aslope (adv.) "on the incline" (late 15c.), from Old English *aslopen, past participle of aslupan "to slip away," from a- "away" + slupan "to slip" (see sleeve).
sloppy (adj.): 1727, "muddy," from slop (n.). Meaning "loose, ill-fitting" is first recorded 1825, influenced by slop "loose outer garment" (1376), which is probably from Middle Dutch slop. Hence, also, slop-shop (1723). Sloppy Joe was originally "loose-fitting sweater worn by girls" (1942); as a name for a kind of spiced hamburger, it is attested from 1961.
slosh (n.): 1814, "slush, sludge," probably a blend of slush and slop in its Middle English sense of "muddy place."
slosh (v.): "to splash about in mud or wet," 1844, from slosh (n.). Meaning "to pour carelessly" is recorded from 1875. Related: Sloshed; sloshing.
sloshed (adj.): "drunk," c.1900, colloquial, past participle adjective from slosh (v.).
slot (n.1): c.1300, "hollow at the base of the throat above the breastbone," from Old French esclot, of uncertain origin. 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 (n.2): "bar or bolt used to fasten a door, window, etc.," c.1300, from Middle Dutch or Middle Low German slot (cf. Old Norse slot, Old High German sloz, German Schloss "bolt, bar;" Old Saxon slutil "key"), from Proto-Germanic stem *slut- "to close" (cf. Old Frisian sluta, Dutch sluiten, Old High German sliozan, German schliessen "to shut, close"), from PIE root *klau- "hook, peg" (cf. Greek kleis "key;" Latin claudere "to shut, close," clavis "key," clavus "nail;" see close (v.)). Wooden pegs were the original keys.
sloth (n.): late 12c., "indolence, sluggishness," formed from Middle English slou, slowe (see slow); replacing Old English slæwð. 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, from Latin pigritia "laziness" (cf. Spanish perezosa "slothful," also "the sloth").
slothful (adj.): c.1400, from sloth + -ful. Related: Slothfully; slothfulness.
slouch (v.): "walk with a slouch," 1754, from slouch (n.). Related: Slouched; slouching.
slouch (n.): 1510s, "lazy man," variant of slouk (1570), perhaps from Old Norse slokr "lazy fellow," and related to slack on the notion of "sagging, drooping." Meaning "stooping of the head and shoulders" first recorded 1725. Slouch hat first attested 1837.
slough (n.): "muddy place," Old English sloh "soft, muddy ground," of uncertain origin, perhaps from Proto-Germanic *slokhaz. Figurative use, e.g. of moral sunkenness or Bunyan's "Slough of Despond," 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 slughe, slouh "shed skin of a snake" (c.1300), 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." Related: Sloughed; sloughing.
Slovak: 1829, from French Slovak, from the people's own name (cf. Slovak, Czech Slovak, plural Slovaci; Polish Słowak; Russian Slovak; German Slowake).
sloven (n.): mid-15c., "immoral woman," later also "rascal, knave" (regardless of gender); probably from Middle Flemish sloovin "a scold," related to sloef "untidy, shabby," from Proto-Germanic *slup- (cf. Dutch slof "careless, negligent") + Old French suffix -ain, from Latin -anus.
Slovene: 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, cf. Old Church Slavonic Slovene.
slovenly (adj.): 1510s, "low, base, lewd," later "untidy, dirty" (1560s), from sloven + -ly (1).
slow (adj.): Old English slaw "inactive, sluggish," also "not clever," from Proto-Germanic *slæwaz (cf. 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. Slowpoke is first recorded 1848.
slow (v.): Old English slawian, from the source of slow (adj.); modern use may be a 16c. re-formation. Related: Slowed; slowing.
slowdown: 1897, from slow + down.
slubberdegullion (n.): "a slobbering or dirty fellow, a worthless sloven," 1610s, from slubber "to daub, smear" (1520s), probably from Dutch or Low German. Second element appears to be an attempt to imitate French; perhaps related to Old French goalon "a sloven."
sludge (n.): 1640s, possibly from Middle English slutch "mud, mire," or a variant of slush.
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) with reference to its shape. 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."
slug (n.3): "a hard blow," 1830, dialectal, perhaps related to slaughter, slay, etc.
slug (v.): "deliver a hard blow with the fist," 1862, from slug (n.3). Related: Slugged; slugging.
slugabed (n.): 1590s, from obsolete verb slug "be lazy, intert" (early 15c.), which is perhaps from Scandinavian (cf. Swedish dialectal slogga "to be slow or sluggish"); adjective sluggy is from early 13c. With bed (n.).
slugfest (n.): 1916, from slug (n.3) + -fest.
sluggard (n.): late 14c. (implied in sluggardly), from Middle English sluggi "sluggish, indolent," probably from a Scandinavian word, cf. dialectal Norwegian and Swedish slugga "be sluggish," dialectal Norwegian sluggje "heavy, slow person."
'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]
slugger (n.): 1877, originally in baseball, agent noun from slug (v.).