Online Etymology Dictionary

simpliciter: Latin adverb from stem of simplex "simple" (see simplex).
simplicity (n.): late 14c., from Old French simplicite (French simplicité), from Latin simplicitatem (nominative simplicitas) "state of being simple," from simplex (genitive simplicis) "simple" (see simplex). Sense of "ignorance" is from 1510s, that of "plainness" is from 1520s.
simplify (v.): 1650s, from French simplifier "to make simpler" (15c.), from Medieval Latin simplificare "to simplify," from Latin simplex "simple" (see simplex) + root of facere "to make" (see factitious). Meaning "to make easier to do" is from 1759. Related: Simplified; simplifying.
simplistic (adj.): 1881, "trying to explain too much by a single principle," earlier (1860) "of or pertaining to simples" (herbs used in healing; the notion is of medicine of one ingredient only), from simplist "one who studies simples" (1590s); see simple.
simply (adv.): late 13c., simpleliche; see simple + -ly (2). Purely intensive sense is attested from 1580s.
simulacrum (n.): 1590s, from Latin simulacrum "likeness, image, form, representation, portrait," dissimilated from *simulaclom, from simulare "to make like" (see simulation). The word was borrowed earlier as semulacre (late 14c.), via Old French simulacre.
simular (n.): 1520s, "one who simulates," irregularly formed from Latin simulare "to simulate," from stem of similis "like" (see similar). As an adjective, "simulated," from 1610s.
simulate (v.): 1620s (implied in simulated), from Latin simulatus, past participle of simulare (see simulation).
simulated (adj.): "imitative for purposes of experiment or training," 1966 (simulator in the related sense dates from 1947), past participle adjective from simulate (v.).
simulation (n.): mid-14c., "a false show, false profession," from Old French simulation, from Latin simulationem (nominative simulatio) "an imitating, feigning," noun of action from simulare "imitate," from stem of similis "like" (see similar). Meaning "a model or mock-up for purposes of experiment or training" is from 1954.
simulator (n.): 1835, of persons, from Latin simulator "a copier, feigner," agent noun from simulare "imitate," from stem of similis "like" (see similar). In reference to training devices for complex systems, from 1947 (flight simulator).
simulcast (v.): "to broadcast simultaneously on radio and television," 1948, formed from simul(taneous) + (broad)cast. The noun is first recorded 1949, from the verb.
simultaneous (adj.): 1650s, from Late Latin simultaneus, from Latin simul "at the same time" (see similar) + -taneous, abstracted from spontaneous, etc. Related: Simultaneously.
simurgh (n.): monstrous bird, rational and ancient, in Persian mythology, 1786, from Persian simurgh, from Pahlavi sin "eagle" + murgh "bird." Cf. Avestan saeno merego "eagle," Sanskrit syenah "eagle," Armenian cin "kite." Probably identical with the roc (q.v.).
sin (n.): Old English synn "moral wrongdoing, offense against God, misdeed," from Proto-Germanic *sundjo (cf. Old Saxon sundia, Old Frisian sende, Middle Dutch sonde, German Sünde "sin, transgression, trespass, offense"), probably ultimately "true" (cf. Gothic sonjis, Old Norse sannr "true"), from PIE *es-ont-, present participle of root *es- "to be" (see is).

The semantic development is via notion of "to be truly the one (who is guilty)," as in Old Norse phrase verð sannr at "be found guilty of," and the use of the phrase "it is being" in Hittite confessional formula. The same process probably yielded the Latin word sons (genitive sontis) "guilty, criminal" from present participle of sum, esse "to be, that which is." Some etymologists believe the Germanic word was an early borrowing directly from the Latin genitive.

Sin-eater is attested from 1680s. To live in sin "cohabit without marriage" is from 1838. Ice hockey slang sin bin "penalty box" is attested from 1950.
sin (v.): Old English syngian "to commit sin," from synn (see sin (n.)). Cf. Dutch zondigen, German sündigen. Form alt. from Middle English sunigen by influence of the noun.
Sinai: the mountain is perhaps named for Sin, a moon goddess worshipped by Sumerians, Akkadians, and ancient Arabs. As an adjectival form, Sinaic (1769), Sinaitic (1786).
since (adv.): mid-15c., synnes, from sithenes "since," from sithen (plus adverbial genitive -es), from Old English siððan "then, later, after that," originally sið ðan "after that," from sið "after" + ðan, weakened form of ðam, dative of ðæt (see that).

Modern spelling replaced syns, synnes 16c. to indicate voiceless final -s- sound. Old English sið is from PIE *se- "long, late" (see soiree).
sincere (adj.): 1530s, from Middle French sincere, from Latin sincerus (see sincerity). There is no etymological justification for the common story that the word means "without wax" (*sin cerae), and the stories invented to explain that folk etymology are even less plausible.
sincerely (adv.): 1530s, from sincere + -ly (2). As a subscription to letters, recorded from 1702.
sincerity (n.): 1540s, from Middle French sincérité (early 16c.), from Latin sinceritatem (nominative sinceritas), from sincerus "sound, pure, whole," perhaps originally "of one growth" (i.e. "not hybrid, unmixed"), from sem-, sin- "one" + root of crescere "to grow" (see crescent). Ground sense is of "that which is not falsified."
sine (n.): trigonometric function, 1590s (in Thomas Fale's "Horologiographia, the Art of Dialling"), from Latin sinus "fold in a garment, bend, curve." Used mid-12c. by Gherardo of Cremona in Medieval Latin translation of Arabic geometrical text to render Arabic jiba "chord of an arc, sine" (from Sanskrit jya "bowstring"), which he confused with jaib "bundle, bosom, fold in a garment."
sine die: "indefinitely," Latin, literally "without (fixed) day," from sine, enlarged form of sed, se "without" (see secret) + ablative singular of dies "day" (see diurnal).
sine qua non: "an indispensable condition," Latin, literally "without which not," from sine "without" + qua ablative fem. singular of qui "which" + non "not." Feminine to agree with implied causa. The Latin phrase is common in Scholastic use. Sometimes a masculine form, sine quo non, is used when a person is intended. Proper plural is sine quibus non.
sinecure (n.): 1660s, "church benefice without parish duties," from Medieval Latin beneficium sine cura "benefice without care" (of souls), from Latin sine "without," enlarged form of sed, se "without" (see secret) + cura, ablative singular of cura "care" (see cure (n.1)).
sinew (n.): Old English seonowe, oblique form of nominative sionu "sinew," from Proto-Germanic *senawo (cf. Old Saxon sinewa, Old Norse sina, Old Frisian sine, Middle Dutch senuwe, Old High German senawa, German Sehne), from PIE root *sai- "to bend" (cf. Sanskrit snavah "sinew," Avestan snavar, Irish sin "chain").
sinewy (adj.): late 14c., from sinew + -y (2).
sinful (adj.): Old English synnfull; see sin + -ful. Related: Sinfully; sinfulness.
sing (v.): Old English singan "to chant, sing, tell in song," also used of birds (class III strong verb; past tense sang, past participle sungen), from Proto-Germanic *sengwanan (cf. Old Frisian sionga, Middle Dutch singhen, Old High German singan, German singen, Gothic siggwan, Old Norse syngva, Swedish sjunga), from PIE root *sengwh- "to sing, make an incantation."

No related forms in other languages, unless perhaps it is connected to Greek omphe "voice" (especially of a god), "oracle;" and Welsh dehongli "explain, interpret." The typical Indo-European root is represented by Latin canere (see chant (v.)).

Other words meaning "sing" derive from roots meaning "cry, shout," but Irish gaibim is literally "take, seize," with sense evolution via "take up" a song or melody. The criminal slang sense of "to confess to authorities" is attested from 1610s. Singsong (adj.) is first recorded 1734, from earlier use as a noun (c.1600).
Singapore: from Sanskrit Simhapuram "Lion City," from simhah "lion" + puram "city." The name is perhaps metaphoric of something, as no lions are found there. Singapore sling attested from 1930; said on the island to have been invented there 1915 by a barman named Ngian Tong Dron.
singe (v.): Old English sengan "to burn lightly, burn the edges" (of hair, wings, etc.), from Proto-Germanic *sangjanan (cf. Old Frisian of-sendza, Middle Dutch singhen, Dutch zengen, German sengen "to singe"). The root often is said to be related to that of sing, on the idea of some sort of sound produced by singeing. Related: Singed; singeing.
singer (n.): early 14c., agent noun from sing (v.).
Singh: common surname and middle name in North India, later (1699) adopted by Sikhs as a title after their initiation ceremony, also a surname adopted by male Sikhs; 1620s in English, from Hindi Singh, from Sanskrit simhah "lion."
single (adj.): c.1300, "individual, unbroken, unmarried," from Old French sengle "being one, separate," from Latin singulus "one, individual, separate" (usually in plural singuli "one by one"), from sim- (stem of simplus; see simple) + diminutive suffix.

Meaning "unaccompanied or unsupported by others" is from mid-14c. Single-handed is first attested 1709. Single-parent (adj.) is attested from 1969.
single (n.): late 15c., "the middle or outer claw on the foot of a hawk or falcon," from single (adj.). Given various technical meanings from 16c. Sports sense is attested from 1851 (cricket), 1885 (baseball). Meaning "phonograph record with one song on each side" is from 1949. Meaning "unmarried person" is from 1964; singles bar attested from 1969. An earlier word for "unmarried or unattached person" is singleton (1937).
single (v.): "to separate from the herd" (originally in deer-hunting, often with forth or out), 1570s, from single (adj.). Baseball sense of "to make a one-base hit" is attested from 1899 (single (n.) "one-base hit" attested from 1885). Related: Singled; singling.
single-minded (adj.): 1570s, "sincere, honest" (a sense also in single-hearted); meaning "having a single aim or purpose" is from 1860. See single (adj.) + minded. Related: Single-mindedly; single-mindedness.
singlet (n.): "unlined woolen garment," c.1746, from single (adj.) in clothing sense of "unlined, of one thickness" (late 14c.) + -et.
singleton (n.): "single card of a suit in a hand," 1876, originally in whist, from single (adj.).
singly (adv.): c.1300, from single (adj.) + -ly (2).
singspiel (n.): 1876, from German, literally "a singing play," from singen "to sing" + Spiel "a play." Kind of performance popular in Germany late 18c.
singular (adj.): mid-14c., "alone, apart," from Old French singuler "single, separate" (French singulier), from Latin singularis "single, solitary," from singulus (see single (adj.)). Meaning "remarkably good, unusual, rare" is from c.1400, though this was a common meaning of Latin singularis.
singularity (n.): mid-14c., "singleness of aim or purpose," from Old French singularité (12c.) or directly from Late Latin singularitas, from singularis (see singular (adj.)). Meaning "fact of being different from others" is c.1500. Mathematical sense of "point at which a function takes an infinite value" is from 1893. Astronomical use is from 1965.
singultus (n.): Latin, "a sob; a speech broken by sobs."
Sinhalese (adj.): "pertaining to Sri Lanka," 1797, from Sanskrit Sinhala "Sri Lanka, Ceylon," from simhala-, literally "of lions," from simhah "lion." As the name of a language spoken there, it is attested from 1801.
Sinic (adj.): "Chinese," 1660s, from Medieval Latin Sinicus, from Sina "China," from Late Latin Sinae (plural) "the Chinese" (see Sino-).
sinical (adj.): "of or relating to sines," 1590s, from sine + -ical.
Sinicism (n.): "Chinese ways, Chinese affectations," 1891; see Sino- + -ism.
sinister (adj.): early 15c., "prompted by malice or ill-will," from Old French sinistre "contrary, unfavorable, to the left," from Latin sinister "left, on the left side" (opposite of dexter), perhaps from root *sen- and meaning properly "the slower or weaker hand" [Tucker], but Buck suggests it's a euphemism (see left (adj.)), connected with the root of Sanskrit saniyan "more useful, more advantageous."

The Latin word was used in augury in the sense of "unlucky, unfavorable" (omens, especially bird flights, seen on the left hand were regarded as portending misfortune), and thus sinister acquired a sense of "harmful, unfavorable, adverse." This was from Greek influence, reflecting the early Greek practice of facing north when observing omens; in genuine Roman auspices, the left was favorable. Bend (not "bar") sinister in heraldry indicates illegitimacy and preserves the literal sense of "on the left side."
sinistral (adj.): late 15c., "unlucky," from Old French sinistral or Medieval Latin *sinistralis, from sinister (see sinister). Meaning "on the left side" is from 1803. Related: Sinistrally.