Online Etymology Dictionary

spectacular (adj.): 1680s, from Latin spectaculum "a sight, show" (see spectacle) + -ar. As a noun, first attested 1890. Related: Spectacularly.
spectate (v.): "to attend (a sporting event, etc.) to watch, not participate," 1929, back-formation from spectator. Related: Spectated; spectating. Related: Spectation.
spectator (n.): 1580s, from Latin spectator "viewer, watcher," from past participle stem of spectare "to view, watch" (see spectacle). Spectator sport is attested from 1943. Related: Spectatorial. Fem. form spectatress (1630s) is less classically correct than spectatrix (1610s).
specter (n.): c. 1600, "frightening ghost," from French spectre "an image, figure, ghost" (16c.), from Latin spectrum "appearance, vision, apparition" (see spectrum). Figurative sense "object of dread" is from 1774.
spectral (adj.): 1718, "capable of seeing spectres;" 1815, "ghostly;" from spectre + -al (1). Meaning "pertaining to a spectrum" is 1832, from stem of spectrum + -al (1). Related: Spectrally.
spectre (n.): chiefly British English spelling of specter (q.v.); for spelling, see -re.
spectro-: word-forming element meaning "of or by a spectroscope," also "of radiant energy," from comb. form of spectrum.
spectrogram (n.): "photograph of a spectrum," 1890, from spectro- + -gram.
spectrograph (n.): 1876, from spectro- + -graph "instrument for recording; something written." Related: Spectrographic; spectrography.
spectrometer (n.): 1863, from German Spectrometer (Moritz Meyerstein, 1863); see spectro- + -meter.
spectroscope (n.): 1861, from spectro- + -scope. A Greek-Latin hybrid, both elements from the same PIE root. Related: Spectroscopic; spectroscopy.
spectrum (n.): 1610s, "apparition, specter," from Latin spectrum (plural spectra) "an appearance, image, apparition, specter," from specere "to look at, view" (see scope (n.1)). Meaning "visible band showing the successive colors, formed from a beam of light passed through a prism" first recorded 1670s. Figurative sense of "entire range (of something)" is from 1936.
specular (adj.): 1570s, "reflective" (like a mirror), from Latin specularis, from speculum "a mirror" (see speculum). Meaning "assisting in vision; affording a view" is from 1650s, from Latin speculari "to spy" (see speculation).
speculate (v.): 1590s, "view mentally, contemplate" (transitive), back-formation from speculation. Also formerly "view as from a watchtower" (1610s). Intransitive sense of "pursue truth by conjecture or thinking" is from 1670s. Meaning "to invest money upon risk for the sake of profit" is from 1785. Related: Speculated; speculating.
speculation (n.): late 14c., "intelligent contemplation, consideration; act of looking," from Old French speculacion "close observation, rapt attention," and directly from Late Latin speculationem (nominative speculatio) "contemplation, observation," noun of action from Latin speculatus, past participle of speculari "observe," from specere "to look at, view" (see scope (n.1)).

Meaning "pursuit of the truth by means of thinking" is from mid-15c. Disparaging sense of "mere conjecture" is recorded from 1570s. Meaning "buying and selling in search of profit from rise and fall of market value" is recorded from 1774; short form spec is attested from 1794.
speculative (adj.): late 14c., "contemplative," also "purely scientific, in theory only" (opposed to practical), from Old French speculatif "worth great attention; theoretical," or directly from Late Latin speculativus, from past participle stem of speculari (see speculation). Meaning "given to (financial) speculation" is from 1763. Related: Speculatively.
speculator (n.): 1550s, "one who engages in mental speculation," from Latin speculator "a looker-out, spy, scout, explorer; investigator, examiner," agent noun from speculari (see speculation). The financial sense is from 1778. Formerly also "observer, onlooker," especially "an occult seer" (1650s). Fem. form speculatrix attested from 1610s. Related: Speculatory.
speculum (n.): 1590s, in surgery and medicine, "instrument for rendering a part accessible to observation," from Latin speculum "reflector, looking-glass, mirror" (also "a copy, an imitation"), from specere "to look at, view" (see scope (n.1)). As a type of telescope attachment from 1704.
sped: past tense and past participle of speed (v.); Old English spedde.
speech (n.): Old English spæc "act of speaking; power of speaking; manner of speaking; statement, discourse, narrative, formal utterance; language," variant of spræc, from Proto-Germanic *sprek-, *spek- (source also of Danish sprog, Old Saxon spraca, Old Frisian spreke, Dutch spraak, Old High German sprahha, German Sprache "speech;" see speak (v.))

The spr- forms were extinct in English by 1200. Meaning "address delivered to an audience" first recorded 1580s.
And I honor the man who is willing to sink
Half his present repute for the freedom to think,
And, when he has thought, be his cause strong or weak,
Will risk t' other half for the freedom to speak,
Caring naught for what vengeance the mob has in store,
Let that mob be the upper ten thousand or lower.

[James Russell Lowell, "A Fable for Critics," 1848]
speechify (v.): "talk in a pompous, pontifical way," 1723, from speech + -ify. Related: Speechifying; speechification.
speechless (adj.): Old English spæcleas "permanently mute;" see speech + -less. Meaning "mute by effect of astonishment" is from late 14c. Related: Speechlessly; speechlessness.
speed (n.): Old English sped "success, a successful course; prosperity, riches, wealth; luck; opportunity, advancement," from Proto-Germanic *spodiz (source also of Old Saxon spod "success," Dutch spoed "haste, speed," Old High German spuot "success," Old Saxon spodian "to cause to succeed," Middle Dutch spoeden, Old High German spuoten "to haste"), from PIE *spo-ti-, from root *spe- (1) "to thrive, prosper" (source also of Sanskrit sphayate "increases," Latin sperare "to hope," Old Church Slavonic spechu "endeavor," Lithuanian speju "to have leisure").

Meaning "rapidity of movement, quickness, swiftness" emerged in late Old English (at first usually adverbially, in dative plural, as in spedum feran). Meaning "rate of motion or progress" (whether fast or slow) is from c. 1200. Meaning "gear of a machine" is attested from 1866. Meaning "methamphetamine, or a related drug," first attested 1967, from its effect on users.

Speed limit is from 1879 (originally of locomotives); speed-trap is from 1908. Speed bump is 1975; figurative sense is 1990s. Full speed is recorded from late 14c. Speed reading first attested 1965. Speedball "mix of cocaine and morphine or heroin" is recorded from 1909.
speed (v.): Old English spedan (intransitive) "to succeed, prosper, grow rich, advance," from the stem of speed (n.). Compare Old Saxon spodian, Middle Dutch spoeden "hasten," Old High German spuoton "to succeed, prosper," German sputen "make haste, hurry." Meaning "to go hastily from place to place, move rapidly" is attested from c. 1200. Transitive meaning "cause to advance toward success" is from mid-13c.; that of "send forth with quickness, give a high speed to" is first recorded 1560s; that of "to increase the work rate of" (usually with up) is from 1856. Meaning "drive an automobile too fast" is from 1908. Related: Speeded; sped; speeding.
speed-trap (n.): 1908, from speed (n.) + trap (n.).
speeder (n.): "one who drives fast," 1891, agent noun from speed (v.).
speeding (n.): c. 1300, "success;" c. 1400 "action of aiding;" verbal noun from speed (v.). Meaning "action of driving an automobile too fast" is from 1908. Speeding ticket is from 1940.
Speedo: trademark name of a brand of swimwear, 1928, originally made by McRae Hosiery Manufacturers, Australia. From speed.
speedometer (n.): 1904, from speed + -meter. A Germanic-Greek hybrid and thus much execrated.
[T]he ancient Greeks & Romans knew what speed was, & yet no-one supposes they called it speed, whence it follows that speedo- & speedometer are barbarisms. [Fowler]
The correct classical formation is tachometer.
speedway (n.): 1892, American English, from speed (n.) + way (n.).
speedy (adj.): Old English spedig "prosperous, wealthy," from speed (n.) + -y (2). Meaning "moving swiftly" is from late 14c. Related: Speedily; speediness. Speedy Gonzales, Warner Brothers studios talking cartoon mouse, debuted in a 1953 short directed by Bob McKimson.
spell (v.1): early 14c., "read letter by letter, write or say the letters of;" c. 1400, "form words by means of letters," apparently a French word that merged with or displaced a native Old English one; both are from the same Germanic root, but the French word had evolved a different sense. The native word is Old English spellian "to tell, speak, discourse, talk," from Proto-Germanic *spellam (source also of Old High German spellon "to tell," Old Norse spjalla, Gothic spillon "to talk, tell"), from PIE *spel- (2) "to say aloud, recite."

But the current senses seem to come from Anglo-French espeller, Old French espelir "mean, signify, explain, interpret," also "spell out letters, pronounce, recite," from Frankish *spellon "to tell" or some other Germanic source, ultimately identical with the native word.

Related: Spelled; spelling. In early Middle English still "to speak, preach, talk, tell," hence such expressions as hear spell "hear (something) told or talked about," spell the wind "talk in vain" (both 15c.). Meaning "form words with proper letters" is from 1580s. Spell out "explain step-by-step" is first recorded 1940, American English. Shakespeare has spell (someone) backwards "reverse the character of, explain in a contrary sense, portray with determined negativity."
spell (n.1): Old English spell "story, saying, tale, history, narrative, fable; discourse, command," from Proto-Germanic *spellam (see spell (v.1)). Compare Old Saxon spel, Old Norse spjall, Old High German spel, Gothic spill "report, discourse, tale, fable, myth;" German Beispiel "example." From c. 1200 as "an utterance, something said, a statement, remark;" meaning "set of words with supposed magical or occult powers, incantation, charm" first recorded 1570s; hence any means or cause of enchantment.
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"]
Also in Old English, "doctrine; a sermon; religious instruction or teaching; the gospel; a book of the Bible;" compare gospel.
spell (v.2): "work in place of (another)," 1590s, earlier spele, from Old English spelian "to take the place of, be substitute for, represent," related to gespelia "substitute," of uncertain origin. Perhaps related to spilian "to play" (see spiel). Related: Spelled; spelling.
spell (n.2): 1620s, "a turn of work in place of another," from spell (v.2); compare Old English gespelia "a substitute." Meaning shifted toward "continuous course of work" (1706), probably via notion of shift work (as at sea) where one man or crew regularly "spelled" another. Hence "continuous stretch" of something (weather, etc.), recorded by 1728. Hence also, via the notion in give a spell (1750) "relieve another by taking a turn of work" came the sense "interval of rest or relaxation" (1845), which took the word to a sense opposite what it had at the start.
spell-check (v.): "to use a computer's spell checker application on a document," by 1985, from spell (v.) + check (v.1). The applications themselves date to the late 1970s. Related: Spell-checked; spell-checking.
spellbind (v.): "to bind by or as if by spell," 1808, probably a back-formation from spellbound. Related: Spellbinding; spellbinder.
spellbound (adj.): "to be bound by or as if by a spell," 1742, from spell (n.1) + bound (adj.1) "fastened," past participle of bind (v.).
speller (n.): c. 1200, "a preacher;" mid-15c. apparently in the sense "a person who reads letter by letter;" 1864 of a book to teach orthography. Agent noun from spell (v.1).
spelling (n.): mid-15c., "action of reading letter by letter," verbal noun from spell (v.1). Meaning "manner of forming words with letters" is from 1660s; meaning "a way a word has been spelled" is from 1731. Spelling bee is from 1878 (see bee; earlier spelling match, 1845; the act of winning such a schoolroom contest is described 1854 as to spell (someone) down).
spelt (n.): type of grain, Old English spelt "spelt, corn," perhaps an early borrowing from Late Latin spelta "spelt" (noted as a foreign word), which is perhaps from Germanic *spilt-, from PIE *speld-, extended form of root *spel- (1) "to split, to break off" (probably in reference to the splitting of its husks in threshing); see spill (v.).

The word had little currency in English, and its history is discontinuous. Widespread in Romanic languages (Italian spelta, Spanish espelta, Old French spelte, Modern French épeautre). The word also is widespread in Germanic (Old High German spelta, German Spelt), and a Germanic language is perhaps the source of the Late Latin word.
spelunk (n.): "a cave, cavern, a vault," c. 1300, from Old French spelonque (13c.) or directly from Latin spelunca "a cave, cavern, grotto," from Greek spelynx (accusative spelynga, genitive spelyngos) "a cave, cavern," from spelos "a cave." 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." The verb spelunk "explore caves" and the verbal noun spelunking are attested from 1946 and appear to be back-formations.
Spencer (n.): surname attested from late 13c. (earlier le Despenser, c. 1200), literally "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.

As a 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.
Spencerian (adj.): 1863, pertaining to the penmanship system devised by American penman Platt R. Spencer, the "Father of American Writing" (1800-1864), who c. 1840 began promoting an elliptical cursive style that became the standard U.S. business hand from 1850s to early 20c. It had an assured but joyous elegance lacking in the later Palmer letters. The word also can be a reference to English philosopher Herbert Spencer (1820-1903).
spend (v.): "to pay out or away" (money or wealth), Old English -spendan (in forspendan "use up"), from Medieval Latin spendere, a shortening of Latin expendere "to weigh out money, pay down" (see expend) or possibly of dispendere "to pay out." A general Germanic borrowing (Old High German spendon, German and Middle Dutch spenden, Old Norse spenna). In reference to labor, thoughts, time, etc., attested from c. 1300. Intransitive sense "exhaust, wear (oneself) out" is from 1590s (see spent).
spending (n.): late Old English, verbal noun from spend (v.). Spending-money is from 1590s.
spendthrift (n.): c. 1600, from spend (v.) + thrift (n.) in sense of "savings, profits, wealth." Replaced earlier scattergood (1570s) and spend-all (1550s). From c. 1600 as an adjective.
Spenserian (adj.): 1817, from Edmund Spenser (c. 1552-1599), Elizabethan poet (for the origin of the surname, see Spencer). 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.

"The measure soon ceases to be Spenser's except in its mere anatomy of rhyme-arrangement" [Elton, "Survey of English Literature 1770-1880," 1920]; it is the meter in Butler's "Hudibras," Scott's "Lady of the Lake," and notably the "Childe Harold" of Byron, who found (quoting Beattie) that it allowed him to be "either droll or pathetic, descriptive or sentimental, tender or satirical, as the humour strikes me; for, if I mistake not, the measure which I have adopted admits equally of all these kinds of composition."
spent (adj.): "consumed," mid-15c., past participle adjective from spend. Of time, "passed, over," from 1520s; as "worn out, exhausted from overwork," 1560s.