Etymology
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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" (from PIE root *spek- "to observe").

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.
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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.
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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).
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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.
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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.
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*spek- 
Proto-Indo-European root meaning "to observe."

It forms all or part of: aspect; auspex; auspices; auspicious; bishop; circumspect; conspicuous; despicable; despise; episcopal; especial; espionage; espy; expect; frontispiece; gyroscope; haruspex; horoscope; inspect; inspection; inspector; introspect; introspection; perspective; perspicacious; perspicacity; prospect; prospective; respect; respite; retrospect; scope; -scope; scopophilia; -scopy; skeptic; species; specimen; specious; spectacle; spectacular; spectrum; speculate; speculation; speculum; spice; spy; suspect; suspicion; suspicious; telescope.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit spasati "sees;" Avestan spasyeiti "spies;" Greek skopein "behold, look, consider," skeptesthai "to look at," skopos "watcher, one who watches;" Latin specere "to look at;" Old High German spehhon "to spy," German spähen "to spy."
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theorist (n.)
"one given to theory and speculation," 1590s; see theory + -ist.
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frill (n.)
"wavy ornamental edging," 1801 (with a doubtful attestation from 1590s), of uncertain origin despite much speculation [see OED]; figurative sense of "useless ornament" first recorded 1893. Related: Frills.
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cantrip (n.)
"magical spell," 1719, a Scottish word of uncertain origin; despite much speculation it is unclear even where the word is divided, whether the second element is rope (perhaps a reference to knotted cords as magical devices) or trappa "a step" or some other thing.
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big deal (n.)
from 1860s as "a good deal, a large amount;" by 1878 in financial speculation, originally in California publications; see deal (n.1). As an ironic expression, popular in American English from c. 1965, perhaps a translated Yiddishism (such as a groyser kunst).
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