Online Etymology Dictionary

Segway: trademark name (Segway Inc., Bedford, New Hampshire, U.S.), in use from 2001; according to the company, chosen for similarity to segue on notion of "a smooth transition from one place to another."
seigneur (n.): "feudal landowner in France," 1590s, from Middle French seigneur, from Old French seignor (see seignior).
seignior (n.): "lord of a manor," late 13c., from Old French seignior, from Latin seniorem (nominative senior) "older" (see senior). As a general title for a Frenchman, it dates from 1580s.
seigniorage (n.): mid-15c., from Old French seignorage, from seignor (see seignior).
seine (n.): Old English segne "drag-net," from West Germanic *sagina (cf. Old Saxon and Old High German segina), a West Germanic borrowing of Latin sagena (source of French seine), from Greek sagene "a fishing net," also "a hunting net," of unknown origin.
seismic (adj.): 1858, from Greek seismos "earthquake," from seiein "to shake." Seismological is attested from 1850.
seismo-: word-forming element meaning "earthquake," from comb. form of Greek seismos "earthquake" (see seismic).
seismogram (n.): 1891, from seismo- + -gram.
seismograph (n.): 1858, from seismo- + -graph "instrument for recording; something written," from Greek graphe "writing," from graphein "to write, express by written characters," earlier "to draw, represent by lines drawn" (see -graphy). Related: Seismographic.
seismologist (n.): 1859, from seismology + -ist.
seismology (n.): 1852, from seismo- + -logy. Related: Seismological (1850).
seismometer (n.): 1841, from seismo- + -meter.
seize (v.): mid-13c., from Old French seisir "to put in possession of, to take possession of," from Late Latin sacire, generally held to be from a Germanic source, perhaps from Frankish *sakjan "lay claim to" (cf. Gothic sokjan, Old English secan "to seek;" see seek), or from Proto-Germanic *satjan "to place" (see set (v.)).

Originally a legal term in reference to feudal property holdings or offices. Meaning "to grip with the hands or teeth" is from c.1300; that of "to take possession by force or capture" (of a city, etc.) is from mid-14c. Figurative use, with reference to death, disease, fear, etc. is from late 14c. Meaning "to grasp with the mind" is attested from 1855. Of engines or other mechanisms, attested from 1878. Related: Seized; seizing.
seizure (n.): "act of seizing," late 15c., from seize + -ure. Meaning "sudden attack of illness" is attested from 1779.
sejm (n.): congress of the Polish republic, 1690s, from Polish sejm "assembly," from *syn-imu, literally "a taking together."
selah: 1520s, Hebrew word occurring frequently at the end of verse in Psalter. Supposed to be a liturgical direction, perhaps meaning "pause," or perhaps a musical direction to raise the voice (cf. Hebrew base s-l-l "to raise, lift").
seldom (adv.): Old English seldum, alteration of seldan "rare," on analogy of adverbial dative plurals in -um (e.g. whilom "at one time"), from Proto-Germanic *selda- "strange, rare" (cf. Old Norse sjaldan, Old Frisian selden, Dutch zelden, German selten), perhaps ultimately from the base of self (q.v.).
select (adj.): 1560s, from Latin selectus, past participle of seligere "choose out, select," from se- "apart" (see secret) + legere "to gather, select" (see lecture (n.)). The noun meaning "a selected person or thing" is recorded from c.1600. New England selectman first recorded 1640s.
select (v.): 1560s, from select (n.). Related: Selected; selecting.
selection (n.): mid-17c., from Latin selectionem (nominative selectio), noun of action from past participle stem of seligere (see select). Biological sense is from 1837; applied to actions of breeders, hence use by Darwin (1857).
selective (adj.): 1620s; see select + -ive. Related: Selectively; selectiveness. Selective service is from 1917, American English.
Selene: moon goddess, from Greek selene "moon," related to selas "light, brightness, flame," from PIE root *swel- "to burn" (cf. Sanskrit svargah "heaven," Lithuanian svilti "to singe," Old English swelan "to be burnt up," Middle Low German swelan "to smolder"); related to swelter, sultry.
selenium (n.): element name, Modern Latin, from Greek selene "moon" (see Selene). Named by Berzelius (1818), on analogy of tellurium, with which it had been at first confused, and which was named for the earth. Despite the -ium ending it is not a metal and a more appropriate name selenion has been proposed.
Seleucid: 1803, in reference to dynasty founded in Syria 312 B.C.E. by Seleucus Nicator, general of Alexander. It lasted until 65 B.C.E. The Seleucidan Era, a local reckoning in the East (maintained by Syrian Christians) usually is dated to Sept. 1, 312 B.C.E.
self: Old English self, seolf, sylf "one's own person, same," from Proto-Germanic *selbaz (cf. Old Norse sjalfr, Old Frisian self, Dutch zelf, Old High German selb, German selbst, Gothic silba), Proto-Germanic *selbaz, from PIE *sel-bho-, from root *s(w)e- "separate, apart" (see idiom).
Trying to define yourself is like trying to bite your own teeth. [Alan Watts]
Self-made man first recorded 1832, American English.
self-absorbed (adj.): also self absorbed, 1847, from self + absorbed (see absorb).
self-abuse (n.): c.1600, "self-deception," from self + abuse (n.). As a synonym for "masturbation," it is recorded from 1728; an earlier term was self-pollution (1620s).
self-actualization (n.): 1939, from self + actualization. Popularized, though not coined, by U.S. psychologist and philosopher Abraham H. Maslow. (1908-1970).
self-aggrandizing (adj.): also self aggrandizing, 1856, from self + aggrandizing (see aggrandize).
self-appointed (adj.): also self appointed, 1799, from self + appointed.
self-assertive (adj.): also self assertive, 1837, from self + assertive. Related: Self-assertively; self-assertiveness.
self-assurance (n.): also self assurance, 1590s, from self + assurance.
self-assured (adj.): also self assured, 1711, from self + assured.
self-aware (adj.): also self aware, 1924, from self + aware.
self-awareness (n.): also self awareness, 1880, from self + awareness.
self-centered (adj.): 1670s, "fixed, stationary," from self + center (v.). In reference to persons, "engrossed in the self, with little regard for others," it is recorded from 1783.
self-concept (n.): also self concept, 1934, from self + concept.
self-confidence (n.): also self confidence, 1650s, from self + confidence.
self-confident (adj.): 1610s, from self + confident. Related: self-confidently.
self-conscious (adj.): 1680s, "aware of one's action," a word of the English Enlightenment (Locke was using it by 1690), from self + conscious. Morbid sense of "preoccupied with one's own personality" is attested from 1834 (in J.S. Mill).
self-contained (adj.): also self contained, 1590s, from self + contained (see contain).
self-control (n.): 1711, from self + control. Coined by English moral philosopher Anthony Ashley Cooper Shaftesbury (1671-1713).
self-criticism (n.): 1857, from self + criticism. First attested in George Eliot; communist party sense is attested from 1933.
self-defense (n.): 1650s, "act of defending oneself," first attested in Hobbes, from self + defense. In sports sense, first with reference to fencing (1728), then boxing (1820s).
self-deluded (adj.): also self deluded, 1766, from self + deluded (see delude).
self-deprecating (adj.): also self deprecating, 1958, from self + deprecating (see deprecate).
self-deprecation (n.): also self deprecation, 1924, from self + deprecation.
self-destruct (v.): as a verb, in reference to things, "to destroy itself automatically," from self + destruct, apparently first attested in the U.S. TV series "Mission Impossible" (1966). Self-destructive is recorded from 1650s, and self-destruction "suicide" is attested from 1580s.
self-determination (n.): 1683, "determination of mind," from self + determination. Political sense is attested from 1911, popularized by U.S. President Woodrow Wilson (1856-1924).
self-discipline (n.): also self discipline, 1796, from self + discipline. Related: Self-disciplined.