Online Etymology Dictionary

spell (v.1): "name the letters of," Old English spellian "to tell, speak," infl. by Old French espeller "declare, spell," from Frankish *spellon "to tell;" both Old English and Frankish from Proto-Germanic *spellan (cf. Old High German spellon "to tell," Old Norse spjalla, Gothic spillon "to talk, tell"), from PIE *spel- "to say aloud, recite." Related: Spelled; spelling.

Meaning "write or say the letters of a word" is c.1400, from notion of "read letter by letter, read with difficulty" (c.1300). Spell out "explain step-by-step" is first recorded 1940, American English. Spelling bee is from 1878 (earlier simply spelling, 1860).
spell (n.): "incantation, charm," Old English spell "story, speech," from Proto-Germanic *spellan (cf. Old Norse spjall, Old High German spel, Gothic spill "report, discourse, tale;" German Beispiel "example;" see spell (v.1)). Meaning "set of words with magical powers, incantation, charm" first recorded 1570s.
The term 'spell' is generally used for magical procedures which cause harm, or force people to do something against their will -- unlike charms for healing, protection, etc. ["Oxford Dictionary of English Folklore"]
spell (v.2): "work in place of (another)," Old English spelian "to take the place of," related to gespelia "substitute," of uncertain origin. Perhaps related to spilian "to play" (see spiel). Related: Spelled; spelling. The noun meaning "indefinite period of time" first recorded 1706.
spell check (v.): "to use a computer's spell checker application on a document," by 1985. The applications themselves date to the late 1970s.
spellbind (v.): 1808, from spell (n.) + bind. Related: Spellbinding.
spellbound (adj.): 1799, from spell (n.) + bound (adj.1) "fastened," past participle of bind (v.).
spelt (n.): Old English spelt, perhaps an early borrowing from Late Latin spelta "spelt" (c.400, noted as a foreign word), which is perhaps ultimately from PIE root *spel- "to split, to break off" (probably in reference to the splitting of its husks in threshing), which is related to the root of flint.

The word had little currency in English, and its history is discontinuous. Widespread in Romanic languages (cf. Italian spelta, Spanish espelta, Old French spelte, Modern French épeautre). The word also is widespread in Germanic (cf. Old High German spelta, German Spelt), and a Germanic language is perhaps the source of the Late Latin word.
spelunk (n.): "cave, cavern," c.1300, from Old French spelonque or directly from Latin spelunca "a cave, cavern, grotto," from Greek spelynx (genitive spelyngos). An adjective, speluncar "of a cave" is recorded from 1855.
spelunker (n.): "a cave bug; one who explores caves as a hobby," 1942, agent noun formed from obsolete spelunk "cave, cavern."
Spencer (n.): type of repeating rifle used in the American Civil War, 1863, named for U.S. gunsmith Christopher Spencer, who, with Luke Wheelock, manufactured them in Boston, Mass. The surname is attested from late 13c. (earlier le Despenser, c.1200), and means "one who dispenses or has charge of provisions in a household." Middle English spence meant "larder, pantry," and is short for Old French despense (French dépense) "expense," from despenser "to distribute" (see dispense). Another form of the word is spender, which also has become a surname.
spend (v.): "to pay out or away" (money or wealth), Old English -spendan (in forspendan "use up"), from Latin expendere "to weigh out money, pay down" (see expend). A general Germanic borrowing (cf. Old High German spendon, German and Middle Dutch spenden, Old Norse spenna). In reference to labor, thoughts, time, etc., attested from c.1300.
spendthrift (n.): c.1600, from spend + thrift in sense of "savings, profits, wealth." Replaced earlier scattergood (1570s) and spend-all (1550s).
Spenserian (adj.): 1817, from Edmund Spenser (c.1552-1599), Elizabethan poet. Spenserian stanza, which he employed in the "Faerie Queen," consists of eight decasyllabic lines and a final Alexandrine, with rhyme scheme ab ab bc bcc. For the origin of the surname, see Spencer.
sperate (adj.): of debts, "having some likelihood of recovery," 1550s, from Latin speratus, past participle of sperare "to hope" (see speed (n.)).
sperm (n.): late 14c., probably from Old French esperme, from Late Latin sperma "seed, semen," from Greek sperma "seed," from speirein "to sow, scatter," from PIE *sper- "to strew" (see sprout). Sperm bank is attested from 1963.
sperm whale (n.): 1830, shortening of spermaceti whale (so called because the waxy substance in its head was mistaken for sperm), from spermaceti (1471), from Medieval Latin sperma ceti "sperm of a whale," from Latin sperma (see sperm) + cetus "large sea animal" (see Cetacea). The substance in olden times was credited with medicinal properties, as well as being used for candle oil.
Use ... Sperma Cete ana with redd Wyne when ye wax old. [Sir George Ripley, "The Compound of Alchemy," 1471]
spermatogenesis (n.): 1877, earlier in German, from comb. form of Greek sperma (see sperm) + genesis.
spermatozoa (n.): plural of spermatozoon, 1836, from comb. form of Greek sperma (see sperm) + zoon (see zoo).
spermatozoon (n.): (plural spermatozoa), "male sexual cell," 1836, from Greek spermato-, combining form of sperma (genitive spermatos; see sperm) + zoion "animal" (see zoo)
spermicide (n.): 1929; see sperm + -cide.
spew (v.): Old English spiwan "spew, spit," from Proto-Germanic *spiwanan (cf. Old Saxon spiwan, Old Norse spyja, Old Frisian spiwa, Middle Dutch spien, Dutch spuwen, Old High German spiwan, German speien, Gothic spiewan "to spit"), from PIE *sp(y)eu-, probably ultimately of imitative origin (cf. Latin spuere, Greek ptuein, Old Church Slavonic pljuja, Lithuanian spiauti). Also in Old English as a weak verb, speowan. Related: Spewed; spewing.
spew (n.): "vomited matter," c.1600, from spew (v.).
sphagnum (n.): genus of mosses, 1741, Modern Latin, from Latin sphagnos, a kind of lichen, from Greek sphagnos "a spiny shrub, a kind of moss," of unknown origin.
spheno-: word-forming element meaning "wedge," from comb. form of Greek sphen "wedge," probably cognate with Old Norse spann "splinter," Old English spon "chip of wood" (see spoon (n.)).
sphere (n.): 1530s, restored spelling of Middle English spere (c.1300) "space, conceived as a hollow globe about the world," from Old French espere (13c.), from Latin sphaera "globe, ball, celestial sphere," from Greek sphaira "globe, ball," of unknown origin.

Sense of "ball, body of globular form" is from late 14c. Medieval astronomical meaning "one of the 8 (later 10) concentric, transparent, hollow globes believed to revolve around the earth and carry the heavenly bodies" is from late 14c.; the supposed harmonious sound they made rubbing against one another was the music of the spheres (late 14c.). Meaning "range of something" is first recorded c.1600 (e.g. sphere of influence, 1885, originally in reference to Anglo-German colonial rivalry in Africa). A spherical number (1640s) is one whose powers always terminate in the same digit as the number itself (5,6, and 10 are the only ones).
spherical (adj.): 1520s, from sphere + -ical.
spheroid (n.): 1660s, from Latin sphaeroides, from Greek sphairoeides, from sphaira (see sphere) + -oeides "form" (see -oid).
sphincter (n.): 1570s, from Middle French sphincter, from Late Latin sphincter "contractile muscle," from Greek sphinkter "band, anything that binds tight," from sphingein "to squeeze, bind," of unknown origin. First used in anatomical sense by Galen.
sphinx (n.): early 15c., "monster of Greek mythology," from Latin Sphinx, from Greek Sphinx, literally" the strangler," a back-formation from sphingein "to squeeze, bind" (see sphincter).

Monster, having a lion's (winged) body and a woman's head, that waylaid travelers around Thebes and devoured those who could not answer its questions; Oedipus solved the riddle and the Sphinx killed herself. The proper plural would be sphinges. Transferred sense of "person or thing of mysterious nature" is from c.1600. In the Egyptian sense (usually male and wingless) it is attested from 1570s; specific reference to the colossal stone one near the pyramids as Giza is attested from 1610s.
sphygmomanometer (n.): 1891, from comb. form of Greek sphygmos "pulse," from sphyzein "to beat, throb" + -meter.
spic (n.): derogatory for "Latino person," 1913, from cliche protestation, No spick English. Earlier spiggoty (1910 "speak-a the ..."); the term is said to have originated in Panama during the canal construction. But it also was applied from an early date to Italians, and some have suggested an alteration of spaghetti.
spic-and-span (adj.): 1660s, from spick-and-span-new (1570s), literally "new as a recently made spike and chip of wood," from spick "nail" (see spike (n.1)) + span-new "very new" (c.1300), from Old Norse span-nyr, from spann "chip" + nyr "new." Imitation of Dutch spiksplinter nieuw "spike-splinter new."
Spica (n.): 1728, bright star in constellation Virgo, from Latin, literally "ear of grain," corresponding to Greek stakhys (see spike (n.1)).
spicate: 1660s, from Latin spicatus, past participle of spicare "to furnish with spikes," from spica (see spike (n.1)).
spice (n.): early 13c., from Old French espice, from Late Latin species (plural) "spices, goods, wares," from Latin "kind, sort" (see species). Early druggists recognized four "types" of spices: saffron, clove, cinnamon, nutmeg. Figurative sense of "slight touch or trace of something" is recorded from 1530s. Spice-cake first attested 1520s.
spice (v.): "to season with spices," early 14c. (implied in spiced), from spice (n.).
spicule (n.): 1785, from French spicule, from diminutive of Latin spica (see spike (n.1)).
spicy (adj.): 1560s, from spice + -y (2). Figurative sense of "racy, salacious" dates from 1844. Related: Spiciness.
spider (n.): Old English spiþra, from Proto-Germanic *spenthro (cf. Danish spinder), from *spenwanan "to spin" (see spin). The connection with the root is more transparent in other Germanic cognates (cf. Middle Low German, Middle Dutch, Middle High German, German spinne, Dutch spin "spider").

In literature, often a figure of cunning, skill, and industry as well as poisonous predation. As the name for a type of two-pack solitaire, it is attested from 1890. Another Old English word for the creature was gangewifre "a weaver as he goes," and Middle English also had araine "spider" (14c.-15c., from French). Spider plant is from 1852; spider crab is from 1710; spider monkey is from 1764, so called for its long limbs.
spiderweb (n.): 1530s, from spider + web (n.).
spidery (adj.): 1825, from spider + -y (2).
spiel (n.): "glib speech, pitch," 1896, probably from verb (1894) meaning "to speak in a glib manner," earlier "to play circus music" (1870), from German spielen "to play," from Old High German spilon (cognate with Old English spilian "to play"). The noun also perhaps from German Spiel "play, game."
spiff (v.): "make neat or spruce," 1877 (with up or out), probably from spiffy (q.v.). Related: Spiffed; spiffing.
spiffy (adj.): 1853, of uncertain origin, probably related to spiff "well-dressed man." Spiffing "excellent" was very popular in 1870s slang. Uncertain relationship to spiff (n.) "percentage allowed by drapers to their young men when they effect sale of old fashioned or undesirable stock" (1859), or to spiflicate "confound, overcome completely," a cant word from 1749 preserved in American English slang spiflicated "drunk," first recorded 1906 in O.Henry.
spigot (n.): late 14c., "plug used to stop the hole of a cask," probably from Old French *espigot (cf. Gascony dialect espigot "core of a fruit, small ear of grain"), diminutive of Old Provençal espiga "ear of grain," from Latin spica "ear of grain" (see spike (n.2)). Meaning "valve for controlling the flow of a liquid" is from 1520s.
spike (v.): 1620s, "to fasten with spikes," see spike (n.1). Meaning "To rise in a spike" is from 1958. Military sense (1680s) means "to disable guns by driving a big nail into the touch-hole." Figurative use of this sense is from 1823. Meaning "to lace (a drink) with liquor" is from 1889. Journalism sense of "to kill a story before publication" (1908) is from the metal spindle in which old-time editors filed hard copy of stories after they were set in type, or especially when rejected for publication.
spike (n.1): "large nail," mid-14c., perhaps from Old Norse spik "splinter" (related to Old English spicing "large nail"), from Proto-Germanic *spikaz (cf. Middle Dutch spicher, Dutch spijker "nail," Old English spaca, Old High German speihha "spoke"), from PIE root *spei- "sharp point" (cf. Latin spica "ear of corn," spina "thorn, prickle, backbone," and perhaps pinna "pin" (see pin (n.)); Greek spilas "rock, cliff;" Lettish spile "wooden fork;" Lithuanian speigliai "thorns," spitna "tongue of a buckle," Old English spitu "spit").

But based on gender difficulties in the Germanic words, OED casts doubt on this whole derivation and says the English word may be a borrowing of Latin spica (see spike (n.2)), from the same root. Slang meaning "needle" is from 1923. Meaning "pointed stud in athletic shoes" is from 1832. Electrical sense of "pulse of short duration" is from 1935.
spike (n.2): "ear of grain," late 14c., from Latin spica "ear of grain," related to spina "thorn" (see spike (n.1)).
spikenard (n.): mid-14c., "aromatic substance from an Indian plant," from Medieval Latin spica nardi (see spike (n.2)), rendering Greek nardou stakhys; the second element probably ultimately from Sanskrit nalada-, the name of the plant.
spiky (adj.): 1720, from spike (n.1) + -y (2). Related: Spikiness.