Online Etymology Dictionary

Helga: fem. proper name, from Old Norse Helga, literally "holy," from Proto-Germanic *hailaga, from PIE *kailo- (see health). A doublet of Olga.
heliacal (adj.): "pertaining to the sun" (but used especially of stars, in reference to their becoming visible out of the sun's glare), c. 1600, with -al (1) and Latinized form of Greek heliakos "of the sun," from helios "sun" (see sol). The heliacal year is reckoned from the heliacal rising of Sirius; thus it also is known as the canicular year. Related: Heliacally (1580s).
helical (adj.): "spiral-shaped," c. 1600, from Latin helicem (nominative helix) "spiral" (see helix) + -al (1).
Helicon: mountain in Boeotia, sacred to the Muses, on which arose the fountains of Aganippe and Hippocrene, 1520s, from Latinized form of Greek Helikon, literally "the tortuous mountain," from helix (genitive helikos) "spiral" (see helix). Used allusively in reference to poetic inspiration. Related: Heliconian.
helicopter (n.): 1861, from French hélicoptère "device for enabling airplanes to rise perpendicularly," thus "flying machine propelled by screws." From Greek helix (genitive helikos) "spiral" (see helix) + pteron "wing" (see ptero-).

The idea was to gain lift from spiral aerofoils, and it didn't work. Used by Jules Verne and the Wright Brothers, the word was transferred to helicopters in the modern sense when those were developed in the 1920s. Nativized in Flemish as wentelwiek "with rotary vanes."
Heligoland: island in the North Sea off Germany, from the same source as German heilig "holy" (see holy), in reference to an ancient shrine there.
helio-: word-forming element meaning "sun," from Greek helio-, comb. form of helios "sun" (see sol).
heliocentric (adj.): 1680s, from helio- + -centric.
heliograph (n.): 1848, "instrument for taking photographs of the sun," from helio- "sun" + -graph "something written." Earlier, "a description of the sun" (1706, implied in heliographic). From 1877 as the name of a movable mirror used in signaling. Related: Heliographical.

Heliography (1845) was the word for the product of a type of engraving process by chemical reaction from exposure to sunlight. It also was an early term for what came to be called photography (1840).
heliolatry (n.): 1817, from helio- "sun" + -latry "worship." Related: Heliolater (1828).
heliophobia (n.): 1865, from helio- "sun" + -phobia "fear." Perhaps directly from German (where it was in use 1850s). Related: Heliophobe (1885); heliophobic (1886).
heliotrope (n.): "plant which turns its flowers and leaves to the sun," 1620s, from French héliotrope (14c., Old French eliotrope) and directly from Latin heliotropium, from Greek heliotropion "sundial; heliotropic plant," from helios "sun" (see sol) + tropos "turn" (see trope). In English the word in Latin form was applied c. 1000-1600 to heliotropic plants. Related: Heliotropic.
heliotropism (n.): 1854, from heliotrope + -ism.
heliport (n.): 1944, from helicopter + second element abstracted from airport.
helium (n.): 1868, coined from Greek helios "sun" (see sol), because the element was detected in the solar spectrum during the eclipse of Aug. 18, 1868, by English astronomer Sir Joseph N. Lockyer (1836-1920) and English chemist Sir Edward Frankland (1825-1899). It was not actually obtained until 1895; before then it was assumed to be an alkali metal, hence the ending in -ium.
helix (n.): "a spiral thing," 1560s, originally of the volutes of Corinthian capitals, from Latin helix "spiral, a volute in architecture," from Greek helix (genitive helikos), a word used of anything in a spiral shape (an armlet, a curl of hair, the tendril of a vine, a serpent's coil), which is related to eilein "to turn, twist, roll," from PIE *wel-ik-, from root *wel- (3) "to turn, revolve" (see volvox). The classical plural is helices.
hell (n.): also Hell, Old English hel, helle, "nether world, abode of the dead, infernal regions, place of torment for the wicked after death," from Proto-Germanic *haljo "the underworld" (source also of Old Frisian helle, Old Saxon hellia, Dutch hel, Old Norse hel, German Hölle, Gothic halja "hell"). Literally "concealed place" (compare Old Norse hellir "cave, cavern"), from PIE *kel- (2) "to cover, conceal" (see cell).

The English word may be in part from Old Norse mythological Hel (from Proto-Germanic *halija "one who covers up or hides something"), in Norse mythology the name of Loki's daughter who rules over the evil dead in Niflheim, the lowest of all worlds (nifl "mist"). A pagan concept and word fitted to a Christian idiom. In Middle English, also of the Limbus Patrum, place where the Patriarchs, Prophets, etc. awaited the Atonement. Used in the KJV for Old Testament Hebrew Sheol and New Testament Greek Hades, Gehenna. Used figuratively for "state of misery, any bad experience" since at least late 14c. As an expression of disgust, etc., first recorded 1670s.

To have hell break loose is from 1630s. Expression Hell in a handbasket is attested by 1867, in a context implying use from a few years before, and the notion of going to Heaven in a handbasket is from 1853, implying "easy passage" to the destination. Hell or high water (1874) apparently is a variation of between the devil and the deep blue sea. To wish someone would go to hell is in Shakespeare ("Merchant of Venice"). Snowball's chance in hell "no chance" is from 1931; till hell freezes over "never" is from 1832.

To do something for the hell of it "just for fun" is from 1921. To ride hell for leather is from 1889, originally with reference to riding on horseback. Hell on wheels is from 1843 as the name of a steamboat; its general popularity dates from 1869 in reference to the temporary workers' vice-ridden towns along the U.S. transcontinental railroad. Scottish had hell-wain (1580s) "a phantom wagon seen in the sky at night."
Hell's Kitchen: disreputable, impoverished New York City neighborhood, the name attested from 1879. The phrase was used from at least 1866 as an intensive form of Hell.
Hell's kitchen (American), a horrible slum. Hell's Kitchen, Murderer's Row, and the Burnt Rag are names of localities which form collectively the worst place in New York. [Albert Barrère and Charles G. Leland, "A Dictionary of Slang, Jargon & Cant," 1889]
hell-bent (adj.): also hellbent, "recklessly determined," 1824, U.S., originally slang, from hell + bent (adj.).
hell-fired (adj.): a euphemism for damned attested from 1756. See hellfire.
hell-hole (n.): also hellhole, late 14c., "the pit of Hell," from hell + hole (n.). Meaning "very unpleasant place" is from 1866.
hell-hound (n.): also hellhound, "wicked person, agent of Hell" (c. 1400), from Old English hellehund "Cerberus;" see hell + hound (n.). Similar formation in Dutch helhond, German Höllenhund.
hell-raiser (n.): 1906 (to raise hell "create a ruckus" is from 1847, American English), from hell + agent noun from raise (v.). Related: Hell-raising. Probably not from the U.S. political cry "Kansas should raise less corn and more hell" (1900).
hellacious (adj.): 1930s, college slang, from hell + fanciful ending (see bodacious).
hellbender (n.): large salamander of the Ohio and Mississippi rivers, 1812, supposedly so called for its ugliness. The meaning "reckless debauch, drunken frolic" is from 1889.
hellcat (n.): also hell-cat, "volatile woman," c. 1600, from hell + cat (n.). OED suggests "possibly suggested by Hecat," a spelling of Hecate.
hellebore (n.): late 14c., from Old French ellebore, from Latin elleborus, from Greek helleboros, the name given to various plants of both poisonous and medicinal qualities, reputed to cure madness; of uncertain origin. Perhaps literally "plant eaten by fawns," from Greek ellos/hellos "fawn" (from PIE *elno-, extended form of *el- (2) "red, brown," in animal and tree names; see elk) + bora "food of beasts," from bibroskein "to eat," from PIE root *gwere- (4) "to swallow" (see voracity). Related: Helleboric; helleboraceous.
Hellene (n.): "an ancient Greek," 1660s, from Greek Hellen "a Greek," of unknown origin (see Hellenic).
Hellenic (adj.): "pertaining to Greece," 1640s, from Greek Hellenikos "Hellenic, Greek," from Hellen "a Greek," of unknown origin. Earliest surviving use is by Homer in reference to a Thessalian tribe; traditionally from the name of an eponymous ancestor, Hellen, son of Deucalion. In modern use in the arts, of Greek work from the close of the primitive phase to the time of Alexander the Great or the Roman conquest.
Hellenism (n.): c. 1600, "idiom or expression peculiar to Greek;" see Hellenic + -ism. In sense "culture and ideals of ancient Greece," 1865 (by Matthew Arnold, contrasted with Hebraism).
Hellenistic (adj.): 1706, "of or pertaining to Greece and its culture," from Hellene "an ancient Greek" + -istic. Since 1870s, specifically of Greek culture in the few centuries after Alexander. Related: Hellenistical (1650s). Hellenist "one who uses the Greek language, though not a Greek," is attested from 1610s.
heller (n.): former small coin of Austria and Germany, 1570s, from German Heller, from Middle High German haller, short for haller pfennic "penny coined in Hall" in Swabia (see dollar).
hellfire (n.): also hell-fire, "the fire of Hell, eternal torment," from Old English hellefyr, in which helle is the genitive case of hell. It translates Greek gehenna tou pyros, literally "hell of fire." Also used in Middle English for "erysipelas" (mid-15c.).
hellgate (n.): also Hell-gate, "the entrance to Hell," Old English hellegat; see hell + gate (n.).
hellion (n.): "naughty child or person," 1811, American English, altered (by association with Hell) from Scottish/northern England dialectal hallion "worthless fellow, scamp" (1786), a word of unknown origin. Explained humorously in Irving's "Salmagundi" (1811) as "A deputy scullion employed in regions below to cook up the broth."
hellish (adj.): 1520s, from hell + -ish. Related: Hellishly; hellishness. Earlier in same sense were helli "helly" (late 12c.); hellen "hellish, infernal" (c. 1200), with -en (2); and Old English hellic and hellcund.
hello (interj.): greeting between persons meeting, 1881, alteration of hallo, itself an alteration of holla, hollo, a shout to attract attention, which seems to go back at least to c. 1400. Perhaps from holla! "stop, cease." OED cites Old High German hala, hola, emphatic imperative of halon, holon "to fetch," "used especially in hailing a ferryman." Fowler in the 1920s listed halloo, hallo, halloa, halloo, hello, hillo, hilloa, holla, holler, hollo, holloa, hollow, hullo, and writes, "The multiplicity of forms is bewildering ...."

Its rise to popularity as a greeting (1880s) coincides with the spread of the telephone, where it won out as the word said in answering, over Alexander Graham Bell's suggestion, ahoy. Central telephone exchange operators were known as hello-girls (1889).
Hello, formerly an Americanism, is now nearly as common as hullo in Britain (Say who you are; do not just say 'hello' is the warning given in our telephone directories) and the Englishman cannot be expected to give up the right to say hello if he likes it better than his native hullo. [H.W. Fowler, "A Dictionary of Modern English Usage," 1926]
Hells Angels (n.): motorcycle club, the name first attested 1957. They were called Black Rebels in the 1954 film "The Wild One." Earlier Hell's Angels had been used as the title of a film about World War I air combat (1930).
helluva (adj.): "very bad, infernal; tremendous," 1910, attempt to represent the casual pronunciation of expression hell of a _____, which is attested from 1776 (see hell).
helm (n.1): "instrument by which a ship is steered," from Old English helma "rudder; position of guidance, control," from Proto-Germanic *halbma- (source also of Old Norse hjalm, Old High German helmo, German Helm "handle"), from PIE *kelp- "to hold, grasp" (see helve).
Helm - the handle or tiller, in large ships the wheel, by which the runner is managed; the word is sometimes used with reference to the whole stearing [sic]-gear.
Rudder - that part of the helm which consists of a broad piece of timber, enters the water, and is governed by means of the wheel or tiller.
Tiller - the bar or lever by means of which the rudder of a ship or boat is turned.
[J.H.A. Günther, "English Synonyms Explained & Illustrated," Groningen, 1904]
helm (n.2): "a helmet, a defensive cover for the head," from Old English helm "protection, covering; crown, helmet," from Proto-Germanic *helmaz "protective covering" (Cognates: Old Frisian, Old Saxon, Old High German helm, German Helm, Old Norse hjalmr, Gothic hilms), from PIE *kel- (2) "to cover, to hide" (see cell). Italian elmo, Spanish yelmo are from Germanic.
helmet (n.): mid-15c., perhaps a diminutive of Middle English helm (see helm (n.2)). But Barnhart and OED say from Middle French helmet (Modern French heaume), diminutive of helme "helmet," from the same Germanic source as helm (n.2). "Middle English Dictionary" points to both without making a choice. "Old English helm never became an active term in the standard vocabulary of English" [Barnhart].
helminth (n.): "intestinal worm," 1852, from helmintho-, stem of Greek helmins "parasitic worm," from suffixed form of PIE root *wel- (3) "to turn" (see volvox).
helmsman (n.): 1620s, from genitive of helm (n.1) + man (n.). Related: Helmsmanship.
helot (n.): 1570s (with a capital H-) "Spartan serf," from Greek Heilotes, plural of Heilos, popularly associated with Helos, Laconian town reduced to serfdom by Sparta, but perhaps related to Greek halonai, haliskomai "be captured, be taken, be conquered." In extended use of any person in servile bondage by 1823.
help (v.): Old English helpan "help, support, succor; benefit, do good to; cure, amend" (transitive, class III strong verb; past tense healp, past participle holpen), from Proto-Germanic *helpan (source also of Old Norse hjalpa, Old Frisian helpa, Middle Dutch and Dutch helpen, Old High German helfan, German helfen), from PIE root *kelb- "to help" (source also of Lithuanian selpiu "to support, help").

Intransitive sense, "afford aid or assistance," is from early 13c. Recorded as a cry of distress from late 14c. Sense of "serve someone with food at table" (1680s) is translated from French servir "to help, stead, avail," and led to helping "portion of food." Help yourself as an invitation, in reference to food, etc., is from 1894. Related: Helped (c. 1300). The Middle English past participle holpen survives in biblical and U.S. dialectal use.
help (n.): Old English help (m.), helpe (f.) "assistance, succor," from help (v.). Most Germanic languages also have the noun form, such as Old Norse hjalp, Swedish hjälp, Old Frisian helpe, Dutch hulp, Old High German helfa, German Hilfe. Use of help as euphemism for "servant" is American English, 1640s, originally in New England. Bartlett (1848) describes it as "The common name in New England for servants, and for the operatives in a cotton or woollen factory."
A domestic servant of American birth, and without negro blood in his or her veins ... is not a servant, but a 'help.' 'Help wanted,' is the common heading of advertisements in the North, when servants are required. [Chas. Mackay, "Life and Liberty in America," 1859].
Though help also meant "assistant, helper, supporter" in Middle English (c. 1200).
helper (n.): mid-14c., agent noun from help (v.). Helpestre "a female helper" is recorded from c. 1400. The Old English agent noun was helpend.
helpful (adj.): late 14c., from help (n.) + -ful. Related: Helpfully; helpfulness.
helping (n.): "aid, assistance," late 13c., verbal noun from help (v.). Meaning "act of serving food" is from 1824; that of "a portion of food" is from 1883.