Online Etymology Dictionary

semi-: word-forming element from Latin semi- "half," from PIE *semi- (cf. Sanskrit sami "half," Greek hemi- "half," Old English sam-, Gothic sami- "half"). Old English cognate sam- was used in such compounds as samhal "poor health," literally "half-whole;" samsoden "half-cooked," figuratively "stupid" (cf. half-baked); samcucu "half-dead," literally "half-alive;" and the last survivor of the group, sandblind "dim-sighted" (q.v.). The Latin-derived form has been common in forming native words since 15c.
semi-automatic (adj.): in reference to firearms, 1911, from semi- + automatic (q.v.).
semi-detached (adj.): in reference to houses, 1859, from semi- + past participle of detach (v.).
semi-professional: 1897, from semi- + professional (q.v.).
semiannual (adj.): also semi-annual, 1794, from semi- + annual. Related: Semiannually.
semiarid (adj.): also semi-arid, 1898, from semi- + arid.
semicircle (n.): 1520s, from semi- + circle. Semicircular is attested from early 15c.
semicolon (n.): 1640s, a hybrid coined from Latin semi- (see semi-) + Greek kolon "limb, part" (see colon (n.1)).
semiconductor (n.): 1838, "material whose electrical conductivity is between that of a conductor and that of an insulator," from semi- + conductor. Modern very specific sense is recorded from 1931.
semiconscious (adj.): also semi-conscious, 1839, from semi- + conscious.
semifinal: also semi-final, 1884, from semi- + final.
semimonthly (adj.): also semi-monthly, 1851, from semi- + monthly (see month).
seminal (adj.): late 14c., "of seed or semen," from Old French seminal (14c.), from Latin seminalis, from semen (genitive seminis) "seed" (see semen). Figurative sense of "full of possibilities" is attested from 1630s.
seminar (n.): 1887, from German Seminar "group of students working with a professor," from Latin seminarium "breeding ground, plant nursery" (see seminary). Sense of "meeting for discussion of a subject" first recorded 1944.
seminary (n.): mid-15c., "plot where plants are raised from seeds," from Latin seminarium "plant nursery," figuratively, "breeding ground," from seminarius "of seed," from semen (genitive seminis) "seed" (see semen). Meaning "school for training priests" first recorded 1580s; commonly used for any school (especially academies for young ladies) from 1580s to 1930s. Seminarian "seminary student" is attested from 1580s.
Seminole: 1763, from Creek (Muskogean) simano:li, earlier simalo:ni "wild, untamed, runaway," from American Spanish cimarron (see maroon (v.)).
semiology (n.): 1690s, from Greek semeion "sign" (cf. semiotic) + -ology.
semiotic (adj.): 1620s, of symptoms, from Greek semeiotikos "significant," also "observant of signs," adjective form of semeiosis "indication," from semeioun "to signal, to interpret a sign," from sema "sign" (see semantic). Use in psychology dates to 1923.
semiotics (n.): study of signs and symbols with special regard to function and origin, 1880, from semiotic; also see -ics.
semiprecious (adj.): also semi-precious, 1905, from semi- + precious.
semisweet (adj.): also semi-sweet, 1943, from semi- + sweet.
Semite: 1847, "Jew, Arab, Assyrian, Aramæan," from Modern Latin Semita, from Late Latin Sem "Shem," one of the three sons of Noah (Gen. x:21-30), regarded as the ancestor of the Semites (in the days when anthropology was still bound by the Bible), from Hebrew Shem.
Semitic (adj.): 1797, denoting the language group that includes Hebrew, Arabic, Aramaic, Assyrian, etc.; 1826 as “of or pertaining to Semites,” from Medieval Latin Semiticus, from Semita (see Semite). As a noun, as the name of a linguistic family, from 1813. In non-linguistic use, perhaps directly from German semitisch, first used by German historian August Schlözer, 1781. In recent use often with the specific sense "Jewish," but not historically so limited.
Semitism (n.): 1851, from Semite + -ism.
semitrailer (n.): 1919, from semi- + trailer. Short form semi is attested from 1942.
semiweekly (adj.): also semi-weekly, 1791, from semi- + weekly.
semolina (n.): 1797, alteration of Italian semolino, diminutive of semola "bran," from Latin simila "the finest flour," probably from the same Semitic source as Greek semidalis "the finest flour" (cf. Assyrian samidu, Syrian semida "fine meal").
semper-: word-forming element meaning "always, ever," from Latin semper "one, uniform, same," from PIE *sem- "one, together" (cf. Latin semel "once," similis "like;" see same).
sempiternal (adj.): c.1400, from Old French sempiternel (13c.) or Late Latin sempiternalis, from Latin sempiternus, from semper "always" (see semper-) + æternus "eternal" (see eternal).
senate (n.): c.1200, "legal and administrative body of ancient Rome," from Old French senat or Latin senatus "highest council of the state in ancient Rome," literally "council of elders," from senex (genitive senis) "old man, old" (see senile). Attested from late 14c. in reference to governing bodies of free cities in Europe; of national governing bodies from 1550s; specific sense of upper house of U.S. legislature is recorded from 1775.
senator (n.): c.1200, from Old French senateur, from Latin senator, from senex "old, old man" (see senate). An Old English word for it was folcwita.
senatorial (adj.): 1740, from Latin senatorius, from senatorem (see senator) + -al (1).
Senators: name of the professional baseball team in Washington, D.C., from 1891 to 1971.
send (v.): Old English sendan "send, send forth, throw," from Proto-Germanic *sandijanan (cf. Old Saxon sendian, Old Norse and Old Frisian senda, Middle Low German and Middle Dutch senden, Gothic sandjan), causative form of base *sinþan, denoting "go, journey" (source of Old English sið "way, journey," Old Norse sinn, Gothic sinþs "going, walk, time"), from PIE root *sent- "to head for, go" (cf. Lithuanian siusti "send;" see sense (n.)).

Also used in Old English of divine ordinance (e.g. godsend, from Old English sand "messenger, message," from Proto-Germanic *sandaz "that which is sent"). Slang sense of "to transport with emotion, delight" is recorded from 1932, in American English jazz slang. Send-off "farewell" (especially a funeral) is from 1872.
send-up (n.): "a spoof," British slang, 1958, from earlier verb phrase send up "to mock, make fun of" (1931), from send + up, perhaps a transferred sense of the public school term for "to send a boy to the headmaster" (usually for punishment), which is attested from 1821.
sended: alternative past tense and past participle of send. Attested since late 14c.
sender (n.): c.1200, agent noun from send (v.). In 1930s slang, a popular musician or song.
Seneca: 1610s, from Dutch Sennecas, collective name for the upper N.Y. Iroquois tribes, of uncertain origin, perhaps from a Mahican name for the Oneida or their village. Earlier sinnekens, senakees; form probably influenced by the name of the ancient Roman philosopher.
senescent (adj.): 1650s, from Latin scenescens, present participle of senescere "to grow old," from senex "old" (see senile).
seneschal (n.): late 14c., from Old French seneschal, from Frankish Latin siniscalcus, from Proto-Germanic *sini-skalk "senior servant;" first element cognate with Latin senex "old" (see senile); second element from Proto-Germanic *skalkoz "servant" (cf. Gothic skalks, Old High German scalc, Old English scealc; see marshal).
senile (adj.): 1660s, "suited to old age," from French sénile, from Latin senilis "of old age," from senex (genitive senis) "old, old man," from PIE root *sen- "old" (cf. Sanskrit sanah "old;" Avestan hana- "old;" Old Persian hanata- "old age, lapse of time;" Armenian hin "old;" Greek enos "old, of last year;" Lithuanian senas "old," senis "an old man;" Gothic sineigs "old" (used only of persons), sinistra "elder, senior;" Old Norse sina "dry standing grass from the previous year;" Old Irish sen, Old Welsh hen "old"). Meaning "weak or infirm from age" is first attested 1848.
senility (n.): 1791, from senile + -ity.
senior (adj.): late 13c., from Latin senior "older," comparative of senex (genitive senis) "old," from PIE root *sen- (see senile). Original use in English was as addition to a personal name when father and son had the same name; meaning "higher in rank, longer in service" first recorded 1510s. The Latin word yielded titles of respect in many languages, cf. French sire, Spanish señor, Italian signor. Noun sense of "fourth-year student" is from 1741, from earlier general sense of "advanced student" (1610s). Senior citizen first recorded 1938, American English.
seniority (n.): "priority on office or service," mid-15c.; see senior + -ity.
senna: 1540s, from Modern Latin senna, from Arabic sana. Earlier was sene (c.1400), from French.
senor: 1620s, from Spanish señor, from Latin seniorem (see senior).
senora: 1570s, from Spanish señora, fem. of señor (see senor).
senorita (n.): "a young Spanish lady," 1823, from Spanish señorita, Spanish title corresponding to English "Miss," diminutive of señora (see senora).
senryu: form of Japanese poetry, 1938, from name of Karai Senryu (1718-90), Japanese poet.
Sens: city in north-central France, Roman Senones, the capital of the Gaulish people of the same name.