Online Etymology Dictionary

hydrogen (n.): colorless, gaseous element, 1791, hydrogene, from French hydrogène (Modern Latin hydrogenium), coined 1787 by G. de Morveau, Lavoisier, Berthollet, and Fourcroy from Greek hydr-, stem of hydor "water" (see water (n.1)) + French -gène "producing" (see -gen). So called because it forms water when exposed to oxygen. Nativized in Russian as vodorod; in German, it is wasserstoff, "water-stuff." An earlier name for it in English was Cavendish's inflammable air (1767). Hydrogen bomb first recorded 1947; shortened form H-bomb is from 1950.
hydrogenate (v.): "cause to combine with hydrogen," 1809, from hydrogen + -ate (2). Related: Hydrogenated; hydrogenation.
hydrogeology (n.): also hydro-geology, 1802, from hydro- + geology; modeled on French hydrogéologie.
hydrography (n.): "science of the measurement and description of the sea," 1550s, from hydro- + -graphy. Related: Hydrographic.
hydrology (n.): "the science of water," 1762, from hydro- + -logy. Related: Hydrologist; hydrological (1660s).
hydrolysis (n.): "chemical decomposition by water," 1879, formed in English from hydro- + Greek lysis "a loosening, a dissolution," from lyein "to loosen, dissolve" (see lose). Related: Hydrolitic (1875).
hydrometer (n.): 1670s, from hydro- + meter (n.3). Related: Hydrometric; hydrometry.
hydrophobia (n.): late 14c., idroforbia, "dread of water, aversion to swallowing water," a symptom of rabies in man (sometimes used for the disease itself), from Late Latin hydrophobia, from Greek hydrophobos "dreading water," from hydr-, stem of hydor "water" (see water (n.1)) + phobos "dread, fear" (see phobia). So called because human sufferers show aversion to water and have difficulty swallowing it. In Old English as wæterfyrhtness. Related: Hydrophobe.
hydrophobic (adj.): 1807, from hydrophobia + -ic.
hydroplane (n.): "motorboat that glides on the surface of water," 1895, coined by U.S. engineer Harvey D. Williams ["Sibley Journal of Engineering," Cornell University, vol. X, p.81]; from hydro- + ending from airplane.
hydroplane (v.): by 1908, "to skim the surface of water by use of hydroplanes," from hydroplane (n.). Meaning "skid on a thin layer of water" (especially of automobile tires) first recorded 1962, properly aquaplane (itself from 1961 in this sense). Related: Hydroplaned; hydroplaning.
hydroponics (n.): "process of growing plants without soil," 1937, formed in English from hydro- + -ponics, from Greek ponein "to labor, toil," from ponos "labor" (see span (v.)). Related: Hydroponic (adj.).
hydropower (n.): 1922, from hydro- (short for hydro-electric) + power (n.).
hydropsy (n.): see dropsy.
hydrosphere (n.): "the waters of the Earth's surface," 1870, from hydro- + sphere.
hydrostatic (adj.): "pertaining to the principles of equilibrium of fluids," 1670s, from hydro- "water" + -static "stabilizing" (see -stat). Related: Hydrostatics (1650s); hydrostatical.
hydrotherapy (n.): 1842, from hydro- "water" + therapy. Related: Hydrotherapeutic.
hydrothermal (adj.): "of or pertaining to heated water," 1855, in geology, from hydro- "water" + thermal (adj.).
hydrous (adj.): "containing water," 1812; see hydro- + -ous.
hydroxide (n.): 1830, from French hydroxide; see hydro- + oxide.
Hydrus: 1660s as a fabulous water serpent; 1670s as a southern constellation; from Latin Hydrus, from Greek hydros "water-snake" (see hydra).
hyena (n.): mid-14c., from Old French hiene, from Latin hyaena, from Greek hyaina "hyena," apparently a fem. formation from hys "pig," from PIE *su- "swine" (see sow (n.)). With fem. suffix -aina. So called for its bristles. Applied to cruel, treacherous, and greedy persons since at least 1670s. Adjectival forms that have been attempted in English include hyenaish, hyenaesque, hyenic, hyenine, hyenoid.
hyetal (adj.): "of or relating to rain," 1855, American English, from Greek hyetos "rain" (see hyeto-) + -al (1).
hyeto-: word-forming element in science meaning "rain," from Greek hyetos "rain," from hyein "to rain," from PIE root *seue- (2) "take liquid" (see sup (v.2)).
hygiene (n.): 1670s, from French hygiène, ultimately from Greek hygieine techne "the healthful art," from hygies "healthy, sound, hearty," literally "living well" (personified as the goddess Hygieia), from PIE *eyu-gwie-es- "having a vigorous life," from root *aiw-, *ayu- "vital force, life, long life, eternity; in the prime of life, young" (source of Latin aevus, English ever; see eon). The Greek adjective was used by Aristotle as a noun meaning "health." The difficult spelling in English is a relic of the struggle to render the Greek vowels into French.
hygienic (adj.): 1815, from French hygiénique (1812), from hygiène (see hygiene). The earlier adjective was hygienal (1660s). Related: Hygienics (1836).
hygienist (n.): 1836, "an expert on cleanliness," from hygiene + -ist. Earlier was hygeist (1716). Dental sense is recorded by 1913.
hygro-: word-forming element meaning "wet, moist; moisture," from Greek hygros "wet, moist, fluid."
hygrology (n.): "science of bodily humors," 1787, from French or German hygrologie, which are earlier, or from hygro- "wet, moist; moisture" + -ology.
hygrometer (n.): "instrument for measuring atmospheric moisture," 1660s, from French hygromètre, from Greek hygro- "wet, moist; moisture" (see hygro-) + -meter. Related: Hygrometry; hygrometric.
hygroscope (n.): "device which indicates atmospheric humidity," 1660s, from hygro- "wet, moist; moisture" + -scope. It indicates the presence of moisture but not the amount (which is measured by a hygrometer). Related: Hygroscopic.
Hyksos: c. 1600, 15th dynasty of Egyptian kings (1650-1558 B.C.E.), called "Shepherd Kings," from Greek Hyksos, from Egyptian, explained variously as hiq shasu "ruler of nomads," or heqa khoswe "chief of foreign lands."
hylo-: word-forming element meaning "wood, forest," also "matter," from Greek hylos "a wood, a forest, woodland; wood, firewood, timber; stuff, material," used by Aristotle for "matter" in the philosophical sense; a word of unknown origin.
Hyman: masc. proper name; see Hymie.
hymen (n.): 1610s, from French hymen (16c.), from medical Latin, ultimately from Greek hymen "membrane (especially 'virginal membrane,' as the membrane par excellence); thin skin," from PIE *syu-men-, from root *syu- "to bind, sew" (see sew). Specific modern medical meaning begins with Vesalius in the 1555 edition of "De humani corporis fabrica." Apparently not directly connected to Hymen, the god of marriage, but sharing the same root and in folk etymology supposed to be related. Related: Hymenial.
Hymen: 1580s, Greek god of marriage, represented as a youth carrying a torch and a veil, perhaps etymologically "the joiner," literally "the one who sews" (two together); see hymen. Related: Hymeniac.
hymeneal (adj.): c. 1600, "of or relating to a marriage," with -al (1) + Hymen, Greek god of marriage. Compare Latin hymenaeus, from Greek hymenaios "belonging to wedlock;" also as a noun "wedding, wedding song." As a noun in English, "wedding hymn," from 1717.
hymeno-: word-forming element used in technical and scientific compounds, "membrane," from Greek hymen "membrane" (see hymen).
Hymenoptera: order of insects that includes ants, wasps, and bees, 1773, coined in Modern Latin 1748 by Linnæus from Greek hymen (genitive hymenos) "membrane" (see hymen) + pteron "wing" (see ptero-). Related: Hymenopterous.
hymie (n.): "Jewish male" (derogatory), by early 1980s, apparently originally African-American vernacular, from common Jewish masc. proper name Hymie, a pet form of Hyman, from Hebrew, literally "life" (the masc. counterpart of Eve).
hymn (n.): "religious song," c. 1000, from Old French ymne and Old English ymen, both from Late Latin hymnus "song of praise," from Greek hymnos "festive song or ode in praise of gods or heroes" (also sometimes of mournful songs), used in Septuagint to translate several Hebrew words meaning "song praising God." Possibly a variant of hymenaios "wedding song," from Hymen, Greek god of marriage, or, as per Watkins, from a PIE root *sam- "to sing" (source also of Hittite išhamai "he sings," Sanskrit saman- "hymn, song"). Evidence for the silent -n- dates from at least 1530.
hymnal (n.): c. 1500, imnale, himnale, "hymn-book," from Medieval Latin hymnale (n.), from ymnus, from Latin hymnus "song of praise" (see hymn). As an adjective, "of or pertaining to hymns," attested from 1640s.

Hymnal measure (a quatrain, usually iambic, alternately rhymed) is so called for being the preferred verse form for English hymns (such as "Amazing Grace"). It has been popular in English secular poetry as well, "though it almost always suggests the hymn, directly or ironically" [Miller Williams, "Patterns of Poetry," 1986].
hymnic (adj.): 1580s, from hymn + -ic.
hymnist (n.): 1620s, from hymn + -ist.
hyoid (adj.): "having the form of the Greek capital letter upsilon" (ϒ), 1811, from French hyoïde (16c.), from Modern Latin hyoides, from Greek hyoeides "shaped like the letter U," from hu "letter U" (in later Greek called upsilon) + -oeides "like" (see -oid).
hype (n.): "excessive or misleading publicity or advertising," 1967, American English (the verb is attested from 1937), probably in part a back-formation of hyperbole, but also from underworld slang verb hype "to swindle by overcharging or short-changing" (1926), itself a back-formation from hyper "short-change con man" (1914), from the prefix hyper- meaning "over, to excess."

Also possibly influenced by drug addicts' slang hype, shortening of hypodermic needle (1913). Related: Hyped; hyping. In early 18c., hyp "morbid depression of the spirits" was colloquial for hypochondria (usually as the hyp or the hyps).
hyper (adj.): 1942 as a colloquial shortening of hyperactive.
hyper-: word-forming element meaning "over, above, beyond," and often implying "exceedingly, to excess," from Greek hyper (prep. and adv.) "over, beyond, overmuch, above measure," from PIE *uper "over" (see super-).
hyperactive (adj.): 1852, from hyper- "over, exceedingly, to excess" + active.
hyperactivity (n.): 1852, from hyper- "over, exceedingly, to excess" + activity.