Online Etymology Dictionary

slushy (adj.): 1791, "covered with slush," from slush + -y (2). As slang for "ship's cook," 1859, from slush (n.) "refuse from a cook's galley" (1756). Related: Slushiness.
slut (n.): c. 1400, "a dirty, slovenly, or untidy woman," according to OED "Of doubtful origin," but probably cognate with dialectal German Schlutt "slovenly woman," dialectal Swedish slata "idle woman, slut," and Dutch slodde "slut," slodder "a careless man," but the exact relationship of all these is obscure. Chaucer uses sluttish (late 14c.) in reference to the appearance of an untidy man. Also "a kitchen maid, a drudge" (mid-15c.; hard pieces in a bread loaf from imperfect kneading were called slut's pennies, 18c.).

Specific modern sense of "woman who enjoys sex in a degree considered shamefully excessive" is by 1966. Meaning "woman of loose character, bold hussy" is attested from mid-15c., but the primary association through 18c. was untidiness. Johnson has it (second definition) as "A word of slight contempt to a woman" but sexual activity does not seem to figure into his examples. Playful use of the word, without implication of messiness or loose morals, is attested by 1660s:
My wife called up the people to washing by four o'clock in the morning; and our little girl Susan is a most admirable slut, and pleases us mightily, doing more service than both the others, and deserves wages better. [Pepys, diary, Feb. 21, 1664]
Compare playful use of scamp, etc., for boys. Sometimes used 19c. as a euphemism for bitch to describe a female dog.

There is a group of North Sea Germanic words in sl- that mean "sloppy," and also "slovenly woman" and, less often, "slovenly man," and that tend to evolve toward "woman of loose morals." Compare slattern, also English dialectal slummock "a dirty, untidy, or slovenly person" (1861), variant of slammacks "slatternly woman," said to be from slam "ill-shaped, shambling fellow." Also slammakin (from 1756 as a type of loose gown; 1785 as "slovenly female," 1727 as a character name in Gay's "Beggar's Opera"), with variants slamkin, slammerkin. Also possibly related are Middle Dutch slore "a sluttish woman," Dutch slomp, German schlampe "a slattern."
sluttery (n.): "neglect of cleanliness and order," 1580s, from slut + -ery. From 1841 as "an untidy room."
sluttish (adj.): late 14c., from slut + -ish. Related: Sluttishly; sluttishness.
slutty (adj.): c. 1400, "dirty, slovenly," from slut + -ish.
sly (adj.): c. 1200, "skillful, clever, dexterous," from Old Norse sloegr "cunning, crafty, sly," from Proto-Germanic *slogis (source also of Low German slu "cunning, sly," German schlau), probably from base *slak- "to strike, hit" (see slay (v.)), with an original notion of "able to hit." Compare German verschlagen "cunning, crafty, sly," schlagfertig "quick-witted," literally "strike-ready," from schlagen "to strike." A non-pejorative use of the word lingered in northern English dialect until 20c. On the sly "in secret" is recorded from 1812. Sly-boots "a seeming Silly, but subtil Fellow" is in the 1700 "Dictionary of the Canting Crew."
slyly (adv.): c. 1200, from sly (adj.) + -ly (2).
slyness (n.): mid-14c., from sly (adj.) + -ness.
smack (n.4): "heroin," 1942, American English slang, probably an alteration of schmeck "a drug," especially heroin (1932), from Yiddish schmeck "a sniff."
smack (v.2): "to slap a flat surface with the hand," 1835, from smack (n.) in this sense; perhaps influenced by Low German smacken "to strike, throw," which is likely of imitative origin (compare Swedish smak "slap," Middle Low German smacken, Frisian smakke, Dutch smakken "to fling down," Lithuanian smagiu "to strike, knock down, whip").
smack (n.1): "a taste, flavor, savor" especially a slight flavor that suggests something, from Old English smæc "taste; scent, odor," from Proto-Germanic *smak- (source also of Old Frisian smek, Middle Dutch smæck, Dutch smaak, Old High German smac, German Geschmack, Swedish smak, Danish smag), from a Germanic and Baltic root *smeg- meaning "to taste" (source also of Lithuanian smaguriai "dainties," smagus "pleasing"). Meaning "a trace (of something)" is attested from 1530s.
smack (v.1): "make a sharp noise with the lips," 1550s, probably of imitative origin (see smack (v.2)). With adverbial force, "suddenly, directly," from 1782; extended form smack-dab is attested from 1892, American English colloquial (slap-dab is from 1886).
smack (n.3): single-masted sailboat, 1610s, probably from Dutch or Low German smak "sailboat," perhaps from smakken "to fling, dash" (see smack (v.2)), perhaps so-called from the sound made by its sails. French semaque, Spanish zumaca, Italian semacca probably are Germanic borrowings.
smack (v.3): mid-13c., "to smell (something"); mid-14c., "to taste (something), perceive by taste" (transitive); late 14c. "to have a taste, taste of" (intransitive), from smack (n.1). Compare Old English smæccan "to taste," Old Frisian smakia Middle Dutch smaecken, Old High German smakken "have a savor, scent, or taste," German schmecken "taste, try, smell, perceive." Sometimes also smatch. Now mainly in verbal figurative use smacks of ... (first attested 1590s). "Commonly but erroneously regarded as identical with [smack (n.2)], as if 'taste' proceeds from 'smacking the lips.'" [Century Dictionary]
smack (n.2): "smart, sharp sound made by the lips," 1560s, from smack (v.1). Meaning "a loud kiss" is recorded from c. 1600. Meaning "sharp sound made by hitting something with the flat of the hand" is from c. 1746.
smacker (n.): "money," c. 1918, American English slang, perhaps from smack (v.1) on notion of something "smacked" into the palm of the hand. Extended form smackeroo is attested from 1939.
smaik (n.): "mean or contemptible fellow," mid-15c., Scottish, now archaic, current c. 1450-c. 1900, perhaps cognate with Old High German smeichari, from smeken "to flatter."
small (adj.): Old English smæl "thin, slender, narrow; fine," from Proto-Germanic *smal- "small animal; small" (source also of Old Saxon, Danish, Swedish, Middle Dutch, Dutch, Old High German smal, Old Frisian smel, German schmal "narrow, slender," Gothic smalista "smallest," Old Norse smali "small cattle, sheep"), perhaps from a PIE root *(s)melo- "smaller animal" (source also of Greek melon, Old Irish mil "a small animal;" Old Church Slavonic malu "bad"). Original sense of "narrow" now almost obsolete, except in reference to waistline and intestines.
My sister ... is as white as a lilly, and as small as a wand. [Shakespeare, "Two Gentlemen of Verona," 1591]
Sense of "not large, of little size" developed in Old English. Of children, "young," from mid-13c. Meaning "inferior in degree or amount" is from late 13c. Meaning "trivial, unimportant" is from mid-14c. Sense of "having little property or trade" is from 1746. That of "characterized by littleness of mind or spirit, base, low, mean" is from 1824. As an adverb by late 14c.

Small fry, first recorded 1690s of little fish, 1885 of insignificant people. Small potatoes "no great matter" first attested 1924; small change "something of little value" is from 1902; small talk "chit-chat, trifling conversation" (1751) first recorded in Chesterfield's "Letters." Small world as a comment upon an unexpected meeting of acquaintances is recorded from 1895. Small-arms, indicating those capable of being carried in the hand (contrasted to ordnance) is recorded from 1710.
small (n.): early 13c., "small person or animal," from small (adj.). From c. 1300 as "persons of low rank" (opposed to great); late 15c. as "the small part" of something (such as small of the back, 1530s).
small beer (n.): 1560s, originally "weak beer;" used figuratively of small things or trifling matters. Small with the meaning "of low alcoholic content" is attested from mid-15c.
small-mouth (n.): also smallmouth, 1880, short for small-mouth (black) bass (1878); from small (adj.) + mouth (n.).
small-time (adj.): 1910, originally theater slang for lower-salaried circuits, or ones requiring more daily performances; from noun phrase (also 1910). Compare big time.
small-town (adj.): "unsophisticated, provincial," 1824, from noun phrase, from small (adj.) + town.
smallish (adj.): late 14c., from small (adj.) + -ish.
smallness (n.): late 14c., from small (adj.) + -ness.
smallpox (n.): acute, highly contagious disease, 1510s, small pokkes, as distinguished from great pox "syphilis;" from small-pock "pustule caused by smallpox" (mid-15c.); see small (adj.) + pox. Compare French petite vérole. Fatal in a quarter to a third of unvaccinated cases.
smarm (n.): 1914, from colloquial verb smalm, smarm "to smear, bedaub" (the hair, with pomade), 1847, of unknown origin, perhaps somehow suggestive of the action. Verbal meaning "to smear with flattery" is from 1902.
smarmy (adj.): "smooth and sleek" (1909); "ingratiating, unctuous," 1924, from smarm + -y (2). Related: Smarmily; smarminess.
smart (adj.): late Old English smeart "painful, severe, stinging; causing a sharp pain," related to smeortan (see smart (v.)). Meaning "executed with force and vigor" is from c. 1300. Meaning "quick, active, clever" is attested from c. 1300, from the notion of "cutting" wit, words, etc., or else "keen in bargaining." Meaning "trim in attire" first attested 1718, "ascending from the kitchen to the drawing-room c. 1880" [Weekley]. For sense evolution, compare sharp (adj.).

In reference to devices, the sense of "behaving as though guided by intelligence" (as in smart bomb) first attested 1972. Smarts "good sense, intelligence," is first recorded 1968 (Middle English had ingeny "intellectual capacity, cleverness" (early 15c.)). Smart cookie is from 1948.
smart (v.): Old English smeortan "be painful," from Proto-Germanic *smarta- (source also of Middle Dutch smerten, Dutch smarten, Old High German smerzan, German schmerzen "to pain," originally "to bite"), from PIE *smerd- "pain," an extension of the root *mer- (2) "to rub; to harm" (source also of Greek smerdnos "terrible, dreadful," Sanskrit mardayati "grinds, rubs, crushes," Latin mordere "to bite"). Related: Smarted; smarting.
smart (n.): "sharp pain," c. 1200, from sharp (adj.). Cognate with Middle Dutch smerte, Dutch smart, Old High German smerzo, German Schmerz "pain."
smart aleck (n.): 1865, of unknown origin, perhaps in reference to Aleck Hoag, notorious pimp, thief, and confidence man in New York City in early 1840s [Barnhart]. See smart (adj.). Related: Smart-alecky.
smart money (n.): "money bet by those in the know," 1926, from smart (adj.). The same phrase earlier meant "money paid to sailors, soldiers, workers, etc., who have been disabled while on the job" (1690s), from a noun derivative of smart (v.). Also "money paid to obtain the discharge of a recruit" (1760), hence "money paid to escape some unpleasant situation" (1818). Sometimes in legal use, "damages in excess of injury done."
smart-arse: see smart-ass.
smart-ass: also smartass, 1960 (adj.), 1962 (n.), from smart (adj.) + ass (n.2).
smarten (v.): "to make smart, to spruce up, to improve appearance," 1786, from smart (adj.) in its sense of "spruce, trim" + -en (1). Related: Smartened; smartening.
smartly (adv.): early 13c., "vigorously," from smart (adj.) + -ly (2). Meaning "handsomely" is from 1836.
smartmouth (n.): 1968, from smart (adj.) + mouth (n.).
smartness (n.): c. 1300, "severity," from smart (adj.) + -ness. From 1752 as "trimness," 1800 as "cleverness."
smarty (n.): "would-be witty or clever person," 1854, from smart (n.) + -y (3). Extended form smarty-pants first attested 1939.
smash (v.): 1759, "break to pieces," earlier "kick downstairs" (c. 1700), probably of imitative origin (compare smack (v.), mash (v.), crush (v.)). Meaning "act with crushing force" is from 1813; that of "strike violently" is from 1835. Tennis sense is from 1882. Smash-and-grab (adj.) is first attested 1927.
smash (n.): 1725, "hard blow," from smash (v.). Meaning "broken-up condition" is from 1798; that of "failure, financial collapse" is from 1839. Tennis sense is from 1882. Meaning "great success" is from 1923 ("Variety" headline, Oct. 16, in reference to Broadway productions of "The Fool" and "The Rise of Rosie O'Reilly").
smash-up (n.): "collision," 1841, from verbal phrase; see smash (v.) + up (adv.).
smashed (adj.): 1819, "crushed," past participle adjective from smash (v.). Slang meaning "drunk" is from 1962.
smashing (adj.): 1833, "violently crushing to pieces," present participle adjective from smash (v.). Meaning "pleasing, sensational" is from 1911. Related: Smashingly.
smatch: see smack (n.1); smack (v.3).
smatter (v.): early 15c., "talk idly, chatter; talk ignorantly or superficially," of uncertain origin, perhaps imitative. Similar forms are found in Middle High German smetern "to chatter" and Swedish smattra "to patter, rattle," and compare Danish snaddre "chatter, jabber," Dutch snateren, German schnattern "cackle, chatter, prattle." Related: Smattered; smattering.
smatterer (n.): "one who has but slight or superficial knowledge," 1510s, agent noun from smatter (v.).
smattering (n.): "a slight or superficial knowledge," 1530s, verbal noun from smatter (v.).
smear (v.): Old English smerian, smierwan "to anoint or rub with grease, oil, etc.," from Proto-Germanic *smerwjan "to spread grease on" (source also of Old Norse smyrja "to anoint, rub with ointment," Danish smøre, Swedish smörja, Dutch smeren, Old High German smirwen "apply salve, smear," German schmieren "to smear;" Old Norse smör "butter"), from PIE *smeru- "grease" (source also of Greek myron "unguent, balsam," Old Irish smi(u)r "marrow," Old English smeoru "fat, grease, ointment, tallow, lard, suet," Lithuanian smarsas "fat").

Figurative sense of "assault a public reputation with unsubstantiated charges" is from 1879. Related: Smeared; smearing. Smear-word, one used regardless of its literal meaning but invested with invective, is from 1938.