Online Etymology Dictionary

creep (n.): "a creeping motion," 1818, from creep (v.). Meaning "despicable person" is 1935, American English slang, perhaps from earlier sense of "sneak thief" (1914). Creeper "a gilded rascal" is recorded from c. 1600, and the word also was used of certain classes of thieves, especially those who robbed customers in brothels. The creeps "a feeling of dread or revulsion" first attested 1849, in Dickens.
creep (v.): Old English creopan "to creep" (class II strong verb; past tense creap, past participle cropen), from Proto-Germanic *kreupan (source also of Old Frisian kriapa, Middle Dutch crupen, Old Norse krjupa "to creep"), perhaps from a PIE root *g(e)r- "crooked" [Watkins]. Related: Crept; creeping.
creeper (n.): Old English creopera "one who creeps," agent noun from creep (v.). Also see creep (n.). Meaning "lice" is from 1570s; of certain birds from 1660s; of certain plants from 1620s.
creepy (adj.): 1794, "characterized by creeping," from creep + -y (2). Meaning "having a creeping feeling in the flesh" is from 1831; that of producing such a feeling, the main modern sense, is from 1858. Creepy-crawly is from 1858.
crept: past tense and past participle of creep (v.).
grovel (v.): 1590s, Shakespearean back-formation from groveling "on the face, prostrate" (mid-14c.), also used in Middle English as an adjective but probably really an adverb, from gruffe, from Old Norse grufe "prone" + obsolete adverbial suffix -ling (which survives also as the -long in headlong, sidelong). The Old Norse word is found in liggja à grufu "lie face-down," literally "lie on proneness." Old Norse also had grufla "to grovel," grufa "to grovel, cower, crouch down." The whole group is perhaps related to creep (v.). Related: Groveled; grovelled; groveling; grovelling.
Proserpina: daughter of Ceres and wife of Pluto, Latin (or Etruscan) modification of Greek Persephone, perhaps influenced by Latin proserpere "to creep forth" on notion of the germination of plants.
herpetology (n.): "study of reptiles," 1816, from French herpétologie (18c.), coined from Greek herpeton "reptile," literally "creeping thing," from herpein "to creep" (see serpent) + French -logie (see -logy). Related: Herpetologist; herpetological.
slink (v.): Old English slincan "to creep, crawl" (of reptiles), from Proto-Germanic *slinkan (source also of Swedish slinka "to glide," Dutch slinken "to shrink, shrivel;" related to sling (v.)). Of persons, attested from late 14c. Related: Slinked; slinking.
irreption (n.): "a creeping in," 1590s, from Late Latin irreptionem (nominative irreptio), noun of action from past participle stem of Latin irrepere, from assimilated form of in- "in" (see in- (2)) + repere "to creep" (see reptile).
herpes (n.): late 14c., "any inflammatory, spreading skin condition" (used of shingles, gangrene, etc.), from Latin herpes "a spreading skin eruption," from Greek herpes, the name for the disease shingles, literally "creeping," from herpein "to creep, move slowly" (cognate with Latin serpere "to creep;" see serpent). The condition was not distinguished into specific diseases until early 19c.
sneak (v.): 1550s (implied in sneakish), perhaps from some dialectal survival of Middle English sniken "to creep, crawl" (c. 1200), related to Old English snican "to sneak along, creep, crawl," from Proto-Germanic *sneikanan, which is related to the root of snake (n.). Of feelings, suspicions, etc., from 1748. Transitive sense, "to partake of surreptitiously" is from 1883. Related: Sneaking. Sneak-thief first recorded 1859; sneak-preview is from 1938.
serpent (n.): c. 1300, "limbless reptile," also the tempter in Genesis iii.1-5, from Old French serpent, sarpent "snake, serpent" (12c.), from Latin serpentem (nominative serpens) "snake; creeping thing," also the name of a constellation, from present participle of serpere "to creep," from PIE *serp- "to crawl, creep" (source also of Sanskrit sarpati "creeps," sarpah "serpent;" Greek herpein "to creep," herpeton "serpent;" Albanian garper "serpent").

Used figuratively of things spiral or regularly sinuous, such as a type of musical instrument (1730). Serpent's tongue as figurative of venomous or stinging speech is from mistaken medieval notion that the serpent's tongue was its "sting." Serpent's tongue also was a name given to fossil shark's teeth (c. 1600).
cripple (n.): Old English crypel, related to cryppan "to crook, bend," from Proto-Germanic *krupilaz (source also of Old Frisian kreppel, Middle Dutch cropel, German krüppel, Old Norse kryppill). Possibly also related to Old English creopan "to creep" (creopere, literally "creeper," was another Old English word for "crippled person").
smug (adj.): 1550s, "trim, neat, spruce, smart," possibly an alteration of Low German smuk "trim, neat," from Middle Low German smücken "to adorn" (originally "to dress," secondary sense of words meaning "to creep or slip into"), from the same source as smock. The meaning "having a self-satisfied air" is from 1701, an extension of the sense of "smooth, sleek" (1580s), which was commonly used of attractive women and girls. Related: Smugly; smugness.
smuggler (n.): 1660s, from Low German smuggeln or Dutch smokkelen "to transport (goods) illegally," apparently a frequentative formation of a word meaning "to sneak" (from Proto-Germanic *smuganan; source also of Dutch smuigen "to eat secretly;" Swedish smyg "a lurking-hole," Danish smughandel "contraband trade," Norwegian smjuga, Old English smeogan "to creep"), perhaps literally "to slip (contraband through)," from Proto-Germanic *(s)muk- (see smock).
slick (v.): Old English -slician (in nigslicod "newly made sleek"), from Proto-Germanic *slikojan, from base *slikaz (source also of Old Norse slikr "smooth," Old High German slihhan "to glide," German schleichen "to creep, crawl, sneak," Dutch slijk "mud, mire"), from PIE *sleig- "to smooth, glide, be muddy," from root *(s)lei- "slimy" (see slime (n.)). Related: Slicked; slicking.
scree (n.): "pile of debris at the base of a cliff," 1781, back-formation from screes (plural) "pebbles, small stones," from Old Norse skriða "landslide," from skriða "to creep, crawl;" of a ship, "to sail, glide," also "to slide" (on snow-shoes), from Proto-Germanic *skrithanan (source also of Old English scriþan "to go, glide," Old Saxon skridan, Dutch schrijden, Old High German scritan, German schreiten "to stride").
insinuation (n.): 1520s, "act of making an indirect suggestion;" 1530s, "that which is indirectly suggested," from Middle French insinuation (16c.) or directly from Latin insinuationem (nominative insinuatio) "entrance through a narrow way; an ingratiating oneself," noun of action from past participle stem of insinuare "creep in, intrude, wind one's way into" (see insinuate).
ramp (v.): c. 1300, "to climb; to stand on the hind legs" (of animals), from Old French ramper "to climb, scale, mount" (12c., in Modern French "to creep, crawl"), perhaps from Frankish *rampon "to contract oneself" (compare Old High German rimpfan "to wrinkle," Old English hrimpan "to fold, wrinkle"), via notion of the bodily contraction involved in climbing [Klein], from Proto-Germanic *hrimp- "to contract oneself." Related: Ramped; ramping.
spider-plant (n.): 1823, said to have been discovered on the coast of the Pacific northwest of North America during Cook's third expedition and so-named by the sailors, "from its striking resemblance to a large spider when it first appears above the surface, before the stem begins to rise from the spherical arrangement of the leaves, or the flagellae begin to creep to any distance from among them to the soil around" [Peter Sutherland, "Journal of a Voyage in Baffin's Bay," 1852]; from spider + plant (n.).
snake (n.): Old English snaca, from Proto-Germanic *snakon (source also of Old Norse snakr "snake," Swedish snok, German Schnake "ring snake"), from PIE root *sneg- "to crawl, creeping thing" (source also of Old Irish snaighim "to creep," Lithuanian snake "snail," Old High German snahhan "to creep"). In Modern English, gradually replacing serpent in popular use.

Traditionally applied to the British serpent, as distinguished from the poisonous adder. Meaning "treacherous person" first recorded 1580s (compare Old Church Slavonic gadu "reptile," gadinu "foul, hateful"). Applied from 17c. to various snake-like devices and appliances. Snakes! as an exclamation is from 1839.

Snake eyes in crap-shooting sense is from 1919. Snake-bitten "unlucky" is sports slang from 1957, from a literal sense, perhaps suggesting one doomed by being poisoned. The game of Snakes and Ladders is attested from 1907. Snake charmer is from 1813. Snake pit is from 1883, as a supposed primitive test of truth or courage; figurative sense is from 1941. Phrase snake in the grass is from Virgil's Latet anguis in herba [Ecl. III:93].
insinuate (v.): 1520s, "to covertly and subtly introduce into the mind or heart" (trans.), from Latin insinuatus, past participle of insinuare "to thrust in, push in, make a way; creep in, intrude, bring in by windings and curvings, wind one's way into," from in- "in" (see in- (2)) + sinuare "to wind, bend, curve," from sinus "a curve, winding" (see sinus).

Intransitive meaning "hint obliquely" is from 1560s. Meaning "maneuver (someone or something) into some desired position or condition" is from 1570s. Physical or literal sense of "to introduce tortuously or indirectly" is from 1640s. Related: Insinuated; insinuating.
snail (n.): Old English snægl, from Proto-Germanic *snagila (source also of Old Saxon snegil, Old Norse snigill, Danish snegl, Swedish snigel, Middle High German snegel, dialectal German Schnegel, Old High German snecko, German Schnecke "snail"), from *snog-, variant of PIE root *sneg- "to crawl, creep; creeping thing" (see snake (n.)). The word essentially is a diminutive form of Old English snaca "snake," which literally means "creeping thing." Also formerly used of slugs. Symbolic of slowness since at least c. 1000; snail's pace is attested from c. 1400.
sling (v.): c. 1200, "to knock down" using a sling, later "to throw" (mid-13c.), especially with a sling, from Old Norse slyngva, from Proto-Germanic *slingwanan (source also of Old High German slingan, German schlingen "to swing to and fro, wind, twist;" Old English slingan "to creep, twist;" Old Frisian slinge, Middle Dutch slinge, Old High German slinga, German Schlinge "sling;" Middle Swedish slonga "noose, knot, snare"), from PIE *slengwh "to slide, make slide; sling, throw." Meaning "to hang from one point to another" (as a hammock) is from 1690s. Related: Slung; slinging.
smock (n.): Old English smoc "garment worn by women, corresponding to the shirt on men," from Proto-Germanic *smukkaz (source also of Old Norse smokkr "a smock," but this is perhaps from Old English; Old High German smoccho "smock," a rare word; North Frisian smok "woman's shift," but this, too, perhaps from English).

Klein's sources, Barnhart and the OED see this as connected to a group of Germanic sm- words having to do with creeping or pressing close, such as Old Norse smjuga "to creep (through an opening), to put on (a garment)," smuga "narrow cleft to creep through; small hole;" Old Swedish smog "a round hole for the head;" Old English smugan, smeogan "to creep," smygel "a burrow." Compare also German schmiegen "to cling to, press close, nestle;" and Schmuck "jewelry, adornments," from schmucken "to adorn," literally "to dress up."

Watkins, however, traces it to a possible Germanic base *(s)muk- "wetness," figuratively "slipperiness," from PIE root*meug- "slimy, slippery" (see mucus). Either way, the original notion, then, seems generally to have been "garment one creeps or slips into," by the same pattern that produced sleeve and slip (n.2).

Now replaced by euphemistic shift (n.2); smock was the common word down to 18c., and was emblematic of womanhood generally, as in verb smock "to render (a man) effeminate or womanish" (1610s); smocker "man who consorts with women" (18c.); smock-face "person having a pale, effeminate face" (c. 1600). A smock-race (1707) was an old country pastime, a foot-race for women and girls with a smock as a prize. Modern meaning "woman's or child's loose dress or blouse" is from 1907; sense of "loose garment worn by artists over other clothes" is from 1938.
reptile (n.): late 14c., "creeping or crawling animal," from Old French reptile (early 14c.) and directly from Late Latin reptile, noun use of neuter of reptilis (adj.) "creping, crawling," from rept-, past participle stem of repere "to crawl, creep," from PIE root *rep- "to creep, crawl" (source also of Lithuanian replioju "to creep"). Used of persons of low character from 1749.

Precise scientific use began to develop mid-18c., but the word was used as well at first of animals now known as amphibians, including toads, frogs, salamanders; separation of Reptilia (1835 as a distinct class) and Amphibia took place early 19c.; popular use lagged, and reptile still was used late 18c. with sense "An animal that creeps upon many feet" [Johnson, who calls the scorpion a reptile], sometimes excluding serpents.
And the terrestrial animals may be divided into quadrupeds or beasts, reptiles, which have many feet, and serpents, which have no feet at all. [Locke, "Elements of Natural Philosophy," 1689]

An inadvertent step may crush the snail
That crawls at ev'ning in the public path ;
But he that has humanity, forewarn'd,
Will tread aside, and let the reptile live.
[Cowper, "The Task," 1785]
The Old English word for "reptile" was slincend, related to slink.
swerve (v.): c. 1200, "to depart, go make off; turn away or aside;" c. 1300, "to turn aside, deviate from a straight course;" in form from Old English sweorfan "to rub, scour, file away, grind away," but sense development is difficult to trace. The Old English word is from Proto-Germanic *swerb- (cf Old Norse sverfa "to scour, file," Old Saxon swebran "to wipe off"), from PIE root *swerbh- "to turn; wipe off." Cognate words in other Germanic languages (Old Frisian swerva "to creep," Middle Dutch swerven "to rove, roam, stray") suggests the sense of "go off, turn aside" might have existed in Old English, though unrecorded. Related: Swerved; swerving.
scheme (n.): 1550s, "figure of speech," from Medieval Latin schema "shape, figure, form, appearance; figure of speech; posture in dancing," from Greek skhema (genitive skhematos) "figure, appearance, the nature of a thing," related to skhein "to get," and ekhein "to have, hold; be in a given state or condition," from PIE root *segh- "to hold, to hold in one's power, to have" (source also of Sanskrit sahate "he masters, overcomes," sahah "power, victory;" Avestan hazah "power, victory;" Greek ekhein "to have, hold;" Gothic sigis, Old High German sigu, Old Norse sigr, Old English sige "victory").

The sense "program of action" first is attested 1640s. Unfavorable overtones (selfish, devious) began to creep in early 18c. Meaning "complex unity of coordinated component elements" is from 1736. Color scheme is attested from 1884.