Z Look up Z at Dictionary.com
not a native letter in Old English; in Anglo-French words it represents the "ts" sound (as in Anglo-French fiz, from Latin filius, modern Fitz); from late 13c. it began to be used for the voiced "s" sound and had fully taken that role by 1400. For letter name, see zed.
Thou whoreson Zed, thou vnnecessary Letter. ["King Lear," II.ii.69]
Series of zs to represent a buzzing sound first attested 1852; zees "spell of sleep, a nap" is slang first recorded 1963, American English student slang.
za (n.) Look up za at Dictionary.com
U.S. student slang shortening of pizza, attested from 1968.
Zacchaeus Look up Zacchaeus at Dictionary.com
masc. proper name, from Late Latin Zacchaeus, from Greek Zakkhaios, from Hebrew zakkay, literally "pure, innocent," from zakhah "was clean, was pure."
Zachariah Look up Zachariah at Dictionary.com
masc. proper name, Late Latin Zacharias, from Greek Zakharias, from Hebrew Zekharyahu, literally "the Lord has remembered," from zakhar "he remembered."
zaftig (adj.) Look up zaftig at Dictionary.com
"alluringly plump, curvaceous, buxom," 1937, from Yiddish zaftik, literally "juicy," from zaft "juice," from Middle High German saft "juice" (see sap (n.1)).
zag (v.) Look up zag at Dictionary.com
1793, from zig-zag (q.v.).
zaibatsu Look up zaibatsu at Dictionary.com
1937, from Japanese zaibatsu, from zai "wealth" + batzu "clique."
Zaire Look up Zaire at Dictionary.com
African nation (1971-1997), from an early alternative name of the Congo River, from Kikongo nzai, dialectal form of nzadi "river."
zakat (n.) Look up zakat at Dictionary.com
obligatory Islamic tax for religious purposes, 1802, from Persian zakat, etc., from Arabic zakah.
Zamboni (n.) Look up Zamboni at Dictionary.com
proprietary name for a machine used to resurface ice skating rinks, 1965, trademark of Frank J. Zamboni & Co., Paramount, Calif., claiming use since July 1962.
zany (n.) Look up zany at Dictionary.com
comic performer, 1580s, from French zani, from Italian zani, zanni "a zany, clown," originally Zanni, Venetian dialect variant of Gianni, pet form of Giovanni "John;" thus equivalent to English Jack. A stock character in old comedies, he aped the principal actors.
zany (adj.) Look up zany at Dictionary.com
1610s, from zany (n.). Related: Zanily; zaniness.
Zanzibar Look up Zanzibar at Dictionary.com
island off East Africa, from Zengi, name of a local people, said to mean "black," + Arabic barr "coast, shore." Related: Zanzibari.
zap Look up zap at Dictionary.com
1929 as a sound, 1942 as a verb; a comic strip word (especially from "Buck Rogers in the Twenty-Fifth Century"), of imitative origin. Meaning "erase electronically" is 1982. Related: Zapped; zapping.
zapper (n.) Look up zapper at Dictionary.com
electrical pest-killer, 1970, from zap.
Zarathustra Look up Zarathustra at Dictionary.com
from Avestan Zarathushtra (see Zoroastrian). Related: Zarathustrian.
zarf (n.) Look up zarf at Dictionary.com
"holder for a coffee cup," 1836, from Arabic zarf "vessel."
zeal (n.) Look up zeal at Dictionary.com
"passionate ardor in pursuit of an objective or course of action," late 14c., from Old French zel (Modern French zèle) and directly from Late Latin zelus "zeal, emulation" (source also of Italian zelo, Spanish celo), a Church word, from Greek zelos "ardor, eager rivalry, emulation," "a noble passion" [Liddell & Scott], but also "jealousy;" prom PIE *ya- "to seek, request, desire." From mid-15c. as "devotion."
zealot (n.) Look up zealot at Dictionary.com
early 14c., "member of a militant 1st century Jewish sect which fiercely resisted the Romans in Palestine," from Late Latin zelotes, from Greek zelotes "one who is a zealous follower," from zeloun "to be zealous," from zelos "zeal" (see zeal). Extended sense of "a fanatical enthusiast" first recorded 1630s (earlier in this sense was zelator, mid-15c.).
zealotry (n.) Look up zealotry at Dictionary.com
"excessive or undue zeal, fanaticism," 1650s, from zealot + -ry.
zealous (adj.) Look up zealous at Dictionary.com
1520s, from Medieval Latin zelosus "full of zeal" (source of Italian zeloso, Spanish celoso), from zelus (see zeal). Related: Zealously, zealousness.
zebra (n.) Look up zebra at Dictionary.com
c.1600, from Italian zebra, perhaps via Portuguese, earlier applied to a now-extinct wild ass, of uncertain origin, said to be Congolese [OED], or Amharic [Klein], but perhaps ultimately from Latin equiferus "wild horse," from equus "horse" (see equine) + ferus (see fierce). Related: Zebrine; zebroid.
zebu (n.) Look up zebu at Dictionary.com
Asiatic ox, 1774, from French zebu, ultimately of Tibetan origin. First shown in Europe at the Paris fair of 1752.
Zebulon Look up Zebulon at Dictionary.com
masc. proper name, Biblical son of Jacob by Leah, from Hebrew Zebhulun, from zebhul "a dwelling" + diminutive suffix -on (see Gen. xxx:20).
Zechariah Look up Zechariah at Dictionary.com
masc. proper name, Biblical 11th of the Twelve Prophets; see Zachariah.
zed (n.) Look up zed at Dictionary.com
c.1400, from Middle French zede, from Late Latin zeta, from Greek zeta, from Hebrew zayin, letter name, literally "weapon;" so called in reference to the shape of this letter in ancient Hebrew. U.S. pronunciation zee is first attested 1670s. Other dialectal names for the letter are izzard, ezod, uzzard, and zod.
zee (n.) Look up zee at Dictionary.com
"the letter Z," 1670s, now more common in American English.
zein (n.) Look up zein at Dictionary.com
simple protein obtained from maize and wheat, 1822, from zea, Late Latin name for "spelt," from Greek zeia "one-seeded wheat, barley, corn" (from PIE root *yewo-) + -in (2).
Zeiss (adj.) Look up Zeiss at Dictionary.com
in reference to spy-glasses or binoculars, 1905, from the firm founded by German optical instrument manufacturer Carl Zeiss (1816-1888).
zeitgeist (n.) Look up zeitgeist at Dictionary.com
1848, from German Zeitgeist "spirit of the age," literally "time-spirit," from Zeit "time" (see tide (n.)) + Geist "spirit" (see ghost (n.)).
zek (n.) Look up zek at Dictionary.com
"Russian condemned person in a prison or labor camp," 1968, from Russian zek, probably representing a vocalization of z/k, abbreviation of zaklyuchennyi "prisoner."
Zen (n.) Look up Zen at Dictionary.com
school of Mahayana Buddhism, 1727, from Japanese, from Chinese ch'an, ultimately from Sanskrit dhyana "thought, meditation," from PIE root *dheie- "to see, look" (cognates: Greek sema "sign, mark, token"). As an adjective from 1881.
Zend (n.) Look up Zend at Dictionary.com
1715, "Parsee sacred book" (in full, Zend-Avesta, 1620s), from Old Persian zend, from Pahlavi zand "commentary." First used 1771 in reference to the language of the Zend-Avesta by French scholar Abraham Hyacinthe Anquetil-Duperron (1731-1805).
zenith (n.) Look up zenith at Dictionary.com
"point of the heavens directly overhead at any place," late 14c., from Old French cenith (Modern French zénith), from Medieval Latin cenit, senit, bungled scribal transliterations of Arabic samt "road, path," abbreviation of samt ar-ras, literally "the way over the head." Letter -m- misread as -ni-.

The Medieval Latin word could as well be influenced by the rough agreement of the Arabic term with classical Latin semita "sidetrack, side path" (notion of "thing going off to the side"), from se- "apart" + *mi-ta-, suffixed zero-grade form of PIE root *mei- (1) "to change" (see mutable). Figurative sense of "highest point or state" is from c.1600.
zeno- Look up zeno- at Dictionary.com
late 20c. word-forming element used in reference to the planet Jupiter, from Greek zeno-, comb. form from Zeus (see Zeus; also compare Zenobia).
Zenobia Look up Zenobia at Dictionary.com
fem. proper name, from Greek Zenobia, literally "the force of Zeus," from Zen, collateral form of Zeus, + bia "strength, force," cognate with Sanskrit jya "force, power" (see Jain).
Zenonian (adj.) Look up Zenonian at Dictionary.com
1843, pertaining to one of two Greek thinkers: Zeno of Elea ("Zeno of the Paradoxes," 5c. B.C.E.), who disproved the possibility of motion; and Zeno of Citium (c. 300 B.C.E.), founder of stoicism.
zep (n.) Look up zep at Dictionary.com
abbreviation of zeppelin, attested by 1915.
Zephaniah Look up Zephaniah at Dictionary.com
masc. proper name, Biblical ninth of the prophets, from Hebrew Tzephanyah "the Lord has hidden."
zephyr (n.) Look up zephyr at Dictionary.com
mid-14c., from Old English Zefferus, from Latin Zephyrus (source also of French zéphire, Spanish zefiro, Italian zeffiro), from Greek Zephyros "the west wind" (sometimes personified as a god), probably related to zophos "the west, the dark region, darkness, gloom." Extended sense of "mild breeze" is c.1600. Related: Zephyrean.
zeppelin (n.) Look up zeppelin at Dictionary.com
1900, from German Zeppelin, short for Zeppelinschiff "Zeppelin ship," after Count Ferdinand von Zeppelin (1838-1917), German general who perfected its design. Compare blimp.
zero (n.) Look up zero at Dictionary.com
"figure which stands for naught in the Arabic notation," also "the absence of all quantity considered as quantity," c.1600, from French zéro or directly from Italian zero, from Medieval Latin zephirum, from Arabic sifr "cipher," translation of Sanskrit sunya-m "empty place, desert, naught" (see cipher (n.)).

A brief history of the invention of "zero" can be found here. Meaning "worthless person" is recorded from 1813. As an adjective from 1810. Zero tolerance first recorded 1972, originally U.S. political language. Zero-sum in game theory is from 1944 (von Neumann), indicating that if one player wins X amount the other or others must lose X amount.
zero (v.) Look up zero at Dictionary.com
in zero in, 1944, from zero (n.); the image is from instrument adjustment to a setting of "zero" (1909 in this sense, originally in rifle-shooting). Related: Zeroed; zeroing.
zest (n.) Look up zest at Dictionary.com
1670s, from French zeste "piece of orange or lemon peel used as a flavoring," of unknown origin. Sense of "thing that adds flavor" is 1709; that of "keen enjoyment" first attested 1791.
zestful (adj.) Look up zestful at Dictionary.com
1797, from zest + -ful. Related: Zestfully; zestfulness.
zesty (adj.) Look up zesty at Dictionary.com
1789, from zest + -y (2). Related: Zestily; zestiness.
zeta (n.) Look up zeta at Dictionary.com
sixth letter of the Greek alphabet; see zed.
zetetic (adj.) Look up zetetic at Dictionary.com
"proceeding by inquiry," 1640s, from Modern Latin zeteticus, from Greek zetetikos "searching, inquiring," from zetetos, verbal adjective of zetein "seek for, inquire into." Related: Zetetical.
zeugma (n.) Look up zeugma at Dictionary.com
1580s, "a single word (usually a verb or adjective) made to refer to two or more nouns in a sentence" (but properly applying to only one of them), from Greek zeugma, "a zeugma; that which is used for joining; boat bridge," literally "a yoking," from zeugnynai "to yoke" (see jugular).
Zeus Look up Zeus at Dictionary.com
supreme god of the ancient Greeks and master of the others, 1706, from Greek, from PIE *dewos- "god" (cognates: Latin deus "god," Old Persian daiva- "demon, evil god," Old Church Slavonic deivai, Sanskrit deva-), from root *dyeu- "to gleam, to shine;" also the root of words for "sky" and "day" (see diurnal). The god-sense is originally "shining," but "whether as originally sun-god or as lightener" is not now clear.