The entire entry for X in Johnson's dictionary (1756) is: "X is a letter, which, though found in Saxon words, begins no word in the English language." Most English words beginning in -x- are of Greek origin (see chi) or modern commercial coinages. East Anglian in 14c. showed a tendency to use -x- for initial sh-, sch- (such as xal for shall), which didn't catch on but seems an improvement over the current system. As a symbol of a kiss on a letter, etc., it is recorded from 1765. In malt liquor, XX denoted "double quality" and XXX "strongest quality" (1827). ETD X.2
Algebraic meaning "unknown quantity" (1660 in English, from French), sometimes is said to be from medieval use, originally a crossed -r-, in that case probably from Latin radix (see root (n.)). Other theories trace it to Arabic (Klein), but a more prosaic explanation says Descartes (1637) took x, y, z, the last three letters of the alphabet, for unknowns to correspond to a, b, c, used for known quantities. ETD X.3
Used allusively for "unknown person" from 1797, "something unknown" since 1859. As a type of chromosome, attested from 1902 (first so called in German; Henking, 1891). To designate "films deemed suitable for adults only," first used 1950 in Britain; adopted in U.S. Nov. 1, 1968. The XYZ Affair in American history (1797) involved French agents designated by those letters. ETD X.4
"cross out with an 'X'," 1942, from X. ETD x (v.).2
Mongol city founded by Kublai Khan, 1620s, Englished form of Shang-tu. Sense of "dream place of magnificence and luxury" derives from Coleridge's poem (1816). ETD Xanadu.2
"yellowish," 1817, from French xanthique, from Greek xanthos "yellow" (see xantho-). ETD xanthic (adj.).2
also (incorrectly) Xantippe, late 16c., spouse of Socrates (5c. B.C.E.), the prototype of the quarrelsome, nagging wife. The name is related to the masc. proper name Xanthippos, a compound of xanthos "yellow" (see xantho-) + hippos "horse" (from PIE root *ekwo- "horse"). ETD Xanthippe.2
before vowels xanth-, word-forming element meaning "yellow," from Greek xanthos "yellow" of various shades; used especially of hair and horses, of unknown origin. Used in scientific words; such as xanthein (1857) "soluble yellow coloring matter in flowers," xanthophyll (1838) "yellow coloring matter in autumn leaves." Also Huxley's Xanthochroi (1867) "blond, light-skinned races of Europe" (with ōkhros "pale"). ETD xantho-.2
1857, Modern Latin, from Greek xanthos (see xantho-) + -osis. ETD xanthosis (n.).2
1829, "fair-haired and light-complexioned," from Greek xanthos "yellow," of unknown origin (see xantho-). But the word also was used in 19c. anthropology as "specifying the yellow or Mongoloid type of mankind" [Century Dictionary]. ETD xanthous (adj.).2
"small three-masted vessel," favored by Barbary corsairs but also used in Mediterranean trade, by 1745, from French chébec, from Italian sciabecco, ultimately from Arabic shabbak "a small warship." Altered by influence of cognate Spanish xabeque, which shows the old way of representing the Spanish sound now spelled -j-. ETD xebec (n.).2
"prevention of aliens from settling in Sparta," Greek, literally "expulsion of foreigners," from xenelatein "to expel foreigners," from xenos "stranger" (see xeno-) + elatos, verbal adjective of elaunein "drive, drive away, beat out." ETD xenelasia (n.).2
city in Ohio, from Greek xenia "hospitality, rights of a guest, friendly relation with strangers," literally "state of a guest," from xenos "guest" (from PIE root *ghos-ti- "stranger, guest, host"). Founded 1803 and named by vote of a town meeting, on suggestion of the Rev. Robert Armstrong to imply friendliness and hospitality. ETD Xenia.2
"pertaining to hospitality," 1834, from Greek xenia (see Xenia) + -al (1). Related: Xenially. ETD xenial (adj.).2
before vowels, xen-, word-forming element meaning "strange, foreign; stranger, foreigner," from Greek xenos "a guest, stranger, foreigner, refugee, guest-friend, one entitled to hospitality," cognate with Latin hostis, from PIE root *ghos-ti- "stranger, guest, host." "The term was politely used of any one whose name was unknown" [Liddell & Scott]. ETD xeno-.2
"fertilization by pollen from a different plant," 1877, from xeno- "strange, foreign" + -gamy "fertilization." Related: Xenogamous. ETD xenogamy (n.).2
1894, from xeno- "foreign, strange" + -lith "stone." ETD xenolith (n.).2
gaseous element, 1898, from Greek xenon, neuter of xenos "foreign, strange" (from PIE root *ghos-ti- "stranger, guest, host"); coined by its co-discoverer, Scottish chemist Sir William Ramsay (1852-1916); compare krypton. ETD xenon (n.).2
1922, from xeno- "foreign, strange" + -phile. ETD xenophile (n.).2
1974, from xenophile + -ic. ETD xenophilic (adj.).2
1912, from xenophobia + -ic. ETD xenophobic (adj.).2
1897, from xeno- "foreign, strange" + -phobe. As an adjective from 1908. ETD xenophobe (n.).2
"fear or hatred of strangers or what is foreign," 1880, London Daily News, April 12, in which it is coupled with xenomania, in reference to English attitudes toward the French: ETD xenophobia (n.).2
See xeno- "foreign, strange" + -phobia "fear." It was infrequent in 1890s publications but more common from 1903, influenced by or from French xénophobie (by 1901), xénophobe. Earlier (c. 1884) it meant what is now meant by agoraphobia. ETD xenophobia (n.).3
"excessive dryness of hair," 1706, medical Latin, from Greek xerasia "dryness," from xeros "dry, withered," from PIE root *ksero- "dry" (source also of Latin serenus "clear, unclouded," serescere "become dry;" Greek xeron "dry land;" Old High German serawen, German serben "to dry out"). ETD xerasia (n.).2
Andalusian town (modern Jerez) famous for its wine; see sherry. For first letter, see xebec. ETD Xeres.2
"having little moisture, very dry," 1926; see xero- + -ic. ETD xeric (adj.).2
ending favored in British English for certain words that in U.S. typically end in -ction, such as connexion, complexion, inflexion, as being more true to the Latin rules. ETD -xion.2
before vowels, xer-, word-forming element meaning "dry," from Greek xero-, combining form of xeros "dry, withered" (see xerasia). ETD xero-.2
1848, from xero- + derma. ETD xeroderma (n.).2
"photographic reduplication without liquid developers," 1948, from Greek xeros "dry" (see xerasia) + -ography as in photography. Related: Xerographic. ETD xerography (n.).2
"habit of living on dry food," especially as a form of fasting, 1650s, from xero- "dry" + -phagy "eating" (see -phagous). ETD xerophagy (n.).2
"drought-loving," 1863, from xero- + -philous, from Greek from philos "loving," of uncertain origin. ETD xerophilous (adj.).2
1897, from xero- + Greek phyton "a plant" (see phyto-). ETD xerophyte (n.).2
1952, trademark taken out by Haloid Co. of Rochester, N.Y., for a copying device, from xerography. The verb is first attested 1965, from the noun, despite strenuous objection from the Xerox copyright department. Related: Xeroxed; Xeroxing. ETD Xerox.2
1896, X-rays, translation of German X-strahlen, from X, algebraic symbol for an unknown quantity, + Strahl (plural Strahlen) "beam, ray." Coined 1895 by German scientist Wilhelm Conrad Röntgen (1845-1923), who discovered them, to suggest that the exact nature of the rays was unknown. As a verb by 1899. Meaning "image made using X-rays" is from 1934, earlier in this sense was X-radiograph (1899). ETD X-ray (n.).2
"woody tissue in higher plants," 1875, from German Xylem, coined from Greek xylon "wood" (see xylo-). ETD xylem (n.).2
1851, from Greek xylon "wood" (see xylo-) + -ene. ETD xylene (n.).2
before vowels xyl-, word forming element meaning "wood," from Greek xylon "wood cut and ready for use, firewood, timber; piece of wood; stocks, a plank, beam, or bench," in New Testament, "the Cross," a word of uncertain origin. It seems to correspond with Lithuanian šulas "post, pole, stave," Russian šulo "garden-pole," Serbo-Croatian šulj "block," Old High German sul "style, pole," Gothic sauls "pillar," but the exact relationship is unclear, and Beekes asks, "Was the word taken from a non-IE substrate language?" ETD xylo-.2
1842, from Latinized form of Greek xylophagos "wood-eating;" see xylo- + -phagous. ETD xylophagous (adj.).2
1866, coined from Greek xylon "wood" (see xylo-) + phōnē "a sound" (from PIE root *bha- (2) "to speak, tell, say"). ETD xylophone (n.).2
"surgical instrument for scraping bones," 1680s, from Greek xyster "a graving tool," from xyein "to scrape." Beekes compare Sanskrit ksnauti "to grind, whet, rub," Lithuanian skusti "to shave, plane." Perhaps from a PIE *kes- "to scrape." ETD xyster (n.).2