Online Etymology Dictionary

hexane (n.): paraffin hydrocarbon, 1872, from Greek hex "six" (see six) + chemical suffix -ane. So called for its six carbon atoms.
hexapod (n.): "six-footed insect," 1660s, from Modern Latin hexapod-, stem of hexapodus, from Greek hex "six" (see six) + Greek pod-, stem of pous "foot," from PIE root *ped- (1) "a foot" (see foot (n.)). Greek hexapous (adj.) was used only with reference to poetic meter. As an adjective from 1856.
hexiology (n.): "history of the development and behavior of living beings as affected by their environment," 1882, coined by English biologist St. George Jackson Mivart (1827-1900) from Greek hexis "a state or habit," from ekhein "to have, hold;" in intransitive use, "be in a given state or condition" (see scheme (n.)).
Every living creature has also relations with other living creatures, which may tend to destroy it, or indirectly to aid it, and the various physical forces and conditions exercise their several influences upon it. The study of all these complex relations to time, space, physical forces, other organisms, and to surrounding conditions generally, constitutes the science of hexicology (hexiology?). [Mivart]
hey (interj.): c. 1200 as a call implying challenge, rebuttal, anger, derision; variously spelled in Middle English hei, hai, ai, he, heh. Later in Middle English expressing sorrow, or concern; also a shout of encouragement to hunting dogs. Possibly a natural expression (compare Roman eho, Greek eia, German hei, Old French hay, French eh). In modern use often weakened, expressing pleasure, surprise.
Þa onswerede þe an swiðe prudeliche, `Hei! hwuch wis read of se icudd keiser!' ["St. Katherine of Alexandria," c. 1200]
In Latin, hei was a cry of grief or fear; but heia, eia was an interjection denoting joy.
heyday (n.): also hey-day, late 16c. as an exclamation, an alteration of heyda (1520s), an exclamation of playfulness, cheerfulness, or surprise something like Modern English hurrah; apparently it is an extended form of the Middle English interjection hey or hei (see hey). Compare Dutch heidaar, German heida, Danish heida. Modern sense of "stage of greatest vigor" first recorded 1751 (perhaps from a notion that the word was high-day), and it altered the spelling.
Hezbollah (n.): extremist Shiite group active in Lebanon, founded c. 1982, from Persian hezbollah, Arabic hizbullah, literally "Party of God," from hezb/hizb "party" + allah "God." An adherent is a Hezbollahi. The name of various Islamic groups in modern times, the name itself is attested in English by 1960 in referense to an Indonesian guerilla battalion of 1945 that "grew out of a similarly named organization formed by the Japanese to give training in military drill to young Moslems."
In Modjokuto (like Masjumi itself, Hizbullah was Indonesia-wide but, also like Masjumi, it had little effective central organization) this group was led by the present head of Muhammadijah -- the same man who a year or so before was going to Djakarta for propaganda training and studying to be a kamikaze. [Clifford Geertz, "The Religion of Java," Chicago, 1960]
Hezekiah: masc. proper name, biblical, from Hebrew Hizqiyya, literally "the Lord has strengthened," from hazaq "he was strong, he strengthened" + jah, short for yahweh.
hi (interj.): exclamation of greeting, 1862, American English (first recorded reference is to speech of a Kansas Indian), originally to attract attention (15c.), probably a variant of Middle English hy, hey (late 15c.) which also was an exclamation to call attention. The only definition in the "Century Dictionary" [1902] is "An exclamation of surprise, admiration, etc.: often used ironically and in derision," suggesting the development as a greeting-word mostly took place early 20c.
Even more informal is the widely used 'Hi.' A friendly greeting for people who already know each other, it should never be said in answer to a formal introduction, but it is universally used, and accepted, by the young. ["The New Emily Post's Etiquette," 1922]
Extended form hiya attested from 1940.
hi-de-hi: call-and-response exclamation in singing, by 1933, associated with U.S. bandleader Cabell "Cab" Calloway (1907-1994) and especially his signature song "Minnie the Moocher," which dates from 1931.
Calloway recalled in his autobiography that the song came first and the chorus was later improvised when he forgot the lyrics during a radio broadcast. ["Harlem Renaissance Lives," Oxford, 2009]
hi-fi (adj.): 1947, abbreviation of high-fidelity (1934), a descriptive term of radio receivers in reference to their quality of sound reproduction. Hi as an advertiser's phonetic shortening of high (adj.) is attested by 1914. Fidelity in the sense "faithful reproduction of sound" is from 1878.
hiatal (adj.): 1906, from stem of hiatus + -al (1).
hiatus (n.): 1560s, "break or opening" in a material object, especially in anatomy, from Latin hiatus "opening, aperture, rupture, gap," from past participle stem of hiare "to gape, stand open," from PIE root *ghai- "to yawn, gape" (see yawn (v.)). Sense of "gap or interruption in events, etc.;" "space from which something requisite to completeness is absent" [Century Dictionary] is recorded from 1610s.
hibachi (n.): 1863, from Japanese hibachi "firepot," from hi "fire" + bachi, hachi "bowl, pot," which Watkins derives ultimately from Sanskrit patram "cup, bowl."
hibernacle (n.): "winter residence, that which serves for shelter in winter," 1708, from Latin hibernacula (plural) "winter quarters, tents for winter," which is related to hibernare "to winter, occupy winter quarters" (see hibernation) with instrumentive suffix -culum. The Latin word was used in English in biology from 1690s. Related: Hibernacular.
hibernal (adj.): 1620s (figurative), "pertaining to the later years of life;" literal sense "pertaining to winter" attested from 1640s; from Latin hibernalis "wintry," from hibernus "of winter," from hiems "winter" (see hibernation).
hibernate (v.): "pass the winter in torpidity and seclusion," 1802, probably a back-formation from hibernation. Related: Hibernated; hibernating.
hibernation (n.): 1660s, "action of passing the winter" (of plants, insect eggs, etc.), from Latin hibernationem (nominative hibernatio) "the action of passing the winter," noun of action from past participle stem of hibernare "to winter, pass the winter, occupy winter quarters;" related to hiems "winter," from PIE *gheim- "snow, winter" (source also of Sanskrit heman "in winter," Hittite gimmanza, Greek kheima, Old Church Slavonic zima, Lithuanian žiema "winter"). Meaning "dormant condition of animals" is from 1789.
Hibernia: from Latin Hibernia, the Roman name for Ireland, also in forms Iverna, Juverna, Ierne, etc., all ultimately from Old Celtic *Iveriu "Ireland" (see Irish (n.)). This particular form of the name was altered in Latin as though it meant "land of winter" (see hibernation).
Hibernian: 1630s (adj.), 1709 (n.), "Irish;" see Hibernia + -ian. Related: Hibernianism.
Hibernicism (n.): 1758, "use of a word or phrase considered peculiar to the Irish," from stem of Hibernia "Ireland" + -ism.
hibiscus (n.): 1706, from Latin hibiscum, later hibiscus, "marshmallow plant," from Greek hibiskos "mallow," a word of unknown origin, perhaps from Gaulish.
hic: imitation of the sound of hiccuping, attested by 1883 (see hiccup).
hic et nunc: Latin, literally "here and now," from demonstrative pronominal adjective of place hic "this, here" + nunc "now" (see now).
hic jacet: Latin, hic iacet, "here lies," commonly the first words of Latin epitaphs; from demonstrative pronominal adjective of place hic "this, here" + iacet "it lies," third person singular present indicative of iacere "to lie, rest," related to iacere "to throw" (see jet (v.)).
hiccough: 1620s, a more recent variant of hiccup (q.v.) by mistaken association with cough.
hiccup (n.): 1570s, hickop, earlier hicket, hyckock, "a word meant to imitate the sound produced by the convulsion of the diaphragm" [Abram Smythe Palmer, "Folk-Etymology," London, 1882]. Compare French hoquet, Danish hikke, Persian hikuk, Hindi hichki, etc. Modern spelling first recorded 1788; An Old English word for it was ælfsogoða, so called because hiccups were thought to be caused by elves.
hiccup (v.): 1570s; see hiccup (n.).
hiccups (n.): a bout of hiccupping, by 1723; see hiccup (n.). This often also was called hiccup or the hiccup. An earlier word for it (noun and verb) was yex, imitative, from Old English gesca, geosca.
hick (n.): late 14c., Hikke, a popular pet form of the masc. proper name Richard (compare Hod from Robert, Hodge from Roger). Meaning "awkward provincial person" was established by 1700 (see rube); earlier it was the characteristic name of a hosteler, hackneyman, etc. (late 14c.), perhaps via alliteration. The adjective is recorded by 1914.
A hick town is one where there is no place to go where you shouldn't be. [attributed to U.S. humorist Robert Quillen (1887-1948)]
hickey (n.): "any small gadget," 1909, American English, of unknown origin. For the "love-bite" sense, see hickie.
hickie (n.): "love bite; mark on skin made by biting or sucking during foreplay or sex," 1934; earlier "pimple, skin lesion" (c. 1915); perhaps a sense extension and spelling variation from the earlier word meaning "small gadget, device; any unspecified object" (1909, see hickey and compare doohickey, still used in this sense).
hickory (n.): type of North American tree valued for its edible nuts and tough, flexible wood, 1670s, American English, from Algonquian (perhaps Powhatan), shortening of pockerchicory, pocohicora or a similar word, which is sometimes said to be the name for this species of walnut, but Bright calls it "a milky drink made from hickory nuts." Old Hickory as the nickname of U.S. politician Andrew Jackson is recorded from 1815.
hickscorner (n.): "libertine scoffer at religion and the religious," c. 1530, from the name of the character in a work of that name printed c. 1512 by Wynkyn de Worde; from Hick, the common masc. nickname, + scorner.
Hicksite: 1828, noun and adjective, in reference to a seceding group of American Quakers, from the name of their spiritual leader, Elias Hicks. The remainder of the profession (the minority numerically) were known as Orthodox Friends. The schism occurred in 1827 at the Philadelphia Yearly Meeting. The surname is from Hick, popular pet form of Richard.
About the only way I can tell whether a particular Meeting was Orthodox or Hicksite has to do with clocks and pianos. If these -- particularly a clock -- are present, that Meeting was Hicksite. If not, it was Orthodox. [Francis G. Brown, "Downingtown Friends Meeting," 1999]
hid (adj.): early 13c., past tense and alternative past participle of hide (v.1).
How to entangle, trammel up and snare
Your soul in mine, and labyrinth you there
Like the hid scent in an unbudded rose?
Aye, a sweet kiss -- you see your mighty woes.

[Keats, "Lamia"]
hidage (n.): "tax paid to the king per hide of land," late 12c., from Anglo-Latin hidagium, from hida, the measure of land (from Old English hid; see hide (n.2)); also see -age.
hidalgo (n.): "Spanish nobleman of secondary rank," 1590s, from Spanish hidalgo, from Old Spanish fidalgo, usually explained as a shortened from filho de algo "son" (Latin filus) "of someone" (Latin aliquis); this is perhaps an imitation of Arabic ibn-nas "son of people," a complimentary title. For alteration of f- and h- in Spanish, see hacienda.
hidden (adj.): past participle adjective from hide (v.1); a Middle English formation (Old English had gehydd "hidden") on the model of ride/ridden, etc. As "secret, occult" from 1540s. Hidden persuaders (1957) was Vance Packard's term for ad men.
hiddenness (n.): late 14c., from hidden + -ness.
hide (v.1): Old English hydan (transitive and intransitive) "to hide, conceal; preserve; hide oneself; bury a corpse," from West Germanic *hudjan (source also of Middle Dutch, Middle Low German huden), from suffixed form of PIE *keudh- (source also of Greek keuthein "to hide, conceal"), from root *(s)keu- "to cover, conceal" (see hide (n.1)).
hide (n.1): "skin of a large animal," Old English hyd "a hide, a skin," from Proto-Germanic *hudiz (source also of Old Norse huð, Old Frisian hed, Middle Dutch huut, Dutch huid, Old High German hut, German Haut "skin").

From PIE root *(s)keu- "to cover, conceal" (source also of Sanskrit kostha "enclosing wall," skunati "covers;" Armenian ciw "roof;" Latin cutis "skin," scutum "shield," ob-scurus "dark;" Greek kytos "a hollow, vessel," keutho "to cover, to hide," skynia "eyebrows;" Russian kishka "gut," literally "sheath;" Lithuanian kiautas "husk," kutis "stall;" Old Norse sky "cloud;" Old English sceo "cloud;" Middle High German hode "scrotum;" Old High German scura, German Scheuer "barn;" Welsh cuddio "to hide").

Related prehistorically to Old English verb hydan "to hide" (see hide (v.1)), the common notion being of "covering." The alliterative pairing of hide and hair (often negative, hide nor hair) was in Middle English (early 15c.), but earlier and more common was hide ne hewe, literally "skin and complexion ('hue')" (c. 1200).
hide (n.2): a measure of land (obsolete), Old English hid "hide of land," earlier higid, from hiw- "family," from or related to hiwan "household," hiwo "a husband, master of a household," from Proto-Germanic *hiwido-, from PIE *keiwo- (source also of Latin civis "citizen"), from root *kei- (1) "to lie; bed, couch; beloved, dear" (see cemetery, and compare city).

The notion was of "amount of land needed to feed one free family and dependents," usually 100 or 120 acres, but the amount could be as little as 60, depending on the quality of the land. Often also defined as "as much land as could be tilled by one plow in a year." Translated in Latin as familia.
hide-and-seek (n.): children's game, by 1670s, replaced earlier all hid (1580s). See hide (v.1) + seek (v.). Form hide-and-go-seek recorded from 1767, also hide-and-find (1750). Variant hide-and-coop is from 1827. Also I-spy or hy-spy (1777). Another old name for it was king-by-your-leave (1570s).
hideaway (n.): "small, secluded restaurant, etc.," 1929, from hide (v.1) + away. Earlier it meant "a fugitive person" (1871). Compare runaway, stowaway.
hidebound (adj.): 1550s, from hide (n.1) + past tense of bind (v.). Original reference is to emaciated cattle with skin sticking closely to backbones and ribs; metaphoric sense of "restricted by narrow attitudes, obstinately set in opinion" is first recorded c. 1600. The rare hide-bind (v.) is a back-formation.
hideosity (n.): "a very ugly thing," 1807, from hideous on model of monstrosity, etc.
hideous (adj.): c. 1300, "terrifying, horrible, dreadful," from Anglo-French hidous, Old French hideus, earlier hisdos "hideous, horrible, awful, frightening" (11c.; Modern French hideux), from hisda "horror, fear," perhaps of Germanic origin. The old guess that it comes from Vulgar Latin *hispidosus, from Latin hispidus "shaggy, bristly," "presents numerous difficulties" [OED] and seems now to be generally discredited. Meaning "repulsive" is late 14c.
hideously (adv.): mid-14c., hidousli, from hideous + -ly (2).
hideousness (n.): late 14c., from hideous + -ness.
hideout (n.): also hide-out, "a hiding place," 1885, American English, from hide (v.) + out (adv.). The verbal phrase hide out "conceal (oneself) from the authorities" is attested from 1870, American English (in reference to Northern draft dodgers in the Civil War).