Online Etymology Dictionary

haploid (adj.): 1908, from German haploid (1905), from Greek haplos "single."
haplology (n.): 1895; see haplo- + -logy.
haply (adv.): late 14c., hapliche, from hap + -ly (2).
happen (v.): c.1300, "to come to pass, occur," originally "occur by hap, to have the (good or bad) fortune (to do, be, etc.);" see hap (n.). Replaced Old English gelimpan, gesceon, and Middle English befall. In Middle English fel it hap meant "it happened." Related: Happened; happening.
happening (n.): mid-15c., "chance, luck," from present participle of happen; meaning "occurrence" is 1550s. Sense of "spontaneous event or display" is from 1959 in the argot of artists. Happenings "events" was noted by Fowler as a vogue word from c.1905.
happenstance (n.): 1897, from happening + ending from circumstance.
happify (v.): 1610s, from happy + -ify. Related: Happified.
happily (adv.): mid-14c., "by chance or accident," from happy + -ly (2). Meaning "fortunate, lucky" is late 14c.; that of "appropriately" is from 1570s. Happily ever after recorded by 1853.
happiness (n.): 1520s, "good fortune," from happy + -ness. Meaning "pleasant and contented mental state" is from 1590s. Phrase greatest happiness for the greatest number was in Hutcheson (1725).
happy (adj.): late 14c., "lucky, favored by fortune, prosperous;" of events, "turning out well," from hap (n.) "chance, fortune" + -y (2). Sense of "very glad" first recorded late 14c. Ousted Old English eadig (from ead "wealth, riches") and gesælig, which has become silly. Meaning "greatly pleased and content" is from 1520s. Old English bliðe "happy" survives as blithe. From Greek to Irish, a great majority of the European words for "happy" at first meant "lucky." An exception is Welsh, where the word used first meant "wise."

Used in World War II and after as a suffix (e.g. bomb-happy, flak-happy) expressing "dazed or frazzled from stress." Happy medium is from 1778. Happy ending in the literary sense recorded from 1756. Happy as a clam (1630s) was originally happy as a clam in the mud at high tide, when it can't be dug up and eaten. Happy hunting ground, the reputed Indian paradise, is attested from 1840, American English. Related: Happier; happiest.
happy hour: "early evening period of discount drinks and free hors-d'oeuvres at a bar," first recorded 1961.
happy-go-lucky: also happy go lucky, 1670s as an adverb, "haphazard;" the adjective, of persons, recorded from 1856.
Hapsburg: European dynasty, from German Habsburg, from the name of a castle on the Aar in Switzerland, originally Habichtsburg, literally "Hawk's Castle."
haptic (adj.): "pertaining to the sense of touch," 1890, from Greek haptikos "able to come into contact with," from haptein "to fasten."
haptics (n.): 1895, from haptic; see -ics.
hara-kiri (n.): "suicide by disembowelment," 1856, from Japanese, literally "belly-cutting," the colloquial word for what is formally called seppuku "cut open the stomach;" from hara "belly" + kiri "to cut."
haram: see harem.
harangue (n.): mid-15c., arang, Scottish (in English from c.1600), from Middle French harangue (14c.), from Italian aringo "public square, platform," from a Germanic source ultimately from or including Proto-Germanic *ring "circular gathering" (see ring). Perhaps it is ultimately from Gothic *hriggs (pronounced "hrings"), with the first -a- inserted to ease Romanic pronunciation of Germanic hr- (cf. hamper (n.)). But Barnhart suggests a Germanic compound, hari-hring "circular gathering," literally "army-ring."
harangue (v.): 1650s, from French haranguer, from Middle French harangue (see harangue (n.)). Related: Harangued; haranguing.
harass (v.): 1610s, from French harasser "tire out, vex," possibly from Old French harer "set a dog on," and perhaps blended with Old French harier "to harry, draw, drag" [Barnhart]. Originally "to lay waste, devastate," sense of "distress" is from 1650s. Related: Harassed; harassing.
harassment (n.): 1753, from harass + -ment.
harbinger (n.): late 15c., herbengar "one sent ahead to arrange lodgings" (for a monarch, an army, etc.), alteration of Middle English herberger "provider of shelter, innkeeper" (late 12c.), from Old French herbergeor, from herbergier "provide lodging," from herber "lodging, shelter," from Frankish *heriberga "lodging, inn" (cf. Old Saxon, Old High German heriberga "army shelter," from heri "army" + berga "shelter"); see harbor. Sense of "forerunner" is mid-16c. Intrusive -n- is 15c. (see messenger). As a verb, from 1640s (harbinge "to lodge" is late 15c.).
harbor (n.): "lodging for ships," early 12c., probably from Old English herebeorg "lodgings, quarters," from here "army, host" (see harry) + beorg "refuge, shelter" (related to beorgan "save, preserve;" see bury); perhaps modeled on Old Norse herbergi "room, lodgings, quarters." Sense shifted in Middle English to "refuge, lodgings," then to "place of shelter for ships."
harbor (v.): Old English hereborgian, cognate with Old Norse herbergja, Old High German heribergon, Middle Dutch herbergen; see harbor (n.). Figuratively, of thoughts, etc., from late 14c. Related: Harbored; harboring.
harbour: chiefly British English spelling of harbor (n. and v.); for spelling, see -or.
hard (adj.): Old English heard "solid, firm, not soft," also "severe, rigorous, cruel," from Proto-Germanic *hardu- (cf. Old Saxon and Dutch hard, Old Norse harðr "hard," Old High German harto "extremely, very," German hart, Gothic hardus "hard"), from PIE *kortu-, (cf. Greek kratos "strength," kratys "strong"), from root *kar-/*ker- "hard." Meaning "difficult to do" is from c.1200. The adverb sense was also present in Old English.

Hard of hearing preserves obsolete Middle English sense of "having difficulty in doing something." Hard liquor is 1879, American English (hard drink is from 1810; hard cider is from 1789), and this probably led to hard drugs (1955). Hard facts is from 1887; hard news is from 1938. Hard copy (as opposed to computer record) is from 1964; hard disk is from 1978. Hard up (1610s) is originally nautical, of steering (slang sense of "short of money" is from 1821), as is hard and fast (1680s), of a ship on shore. Hard times "period of poverty" is from 1705.

Hard money (1706) is specie, as opposed to paper. Hence 19c. U.S. hard (n.) "one who advocates the use of metallic money as the national currency" (1844). To play hard to get is from 1945. Hard rock as a pop music style recorded from 1967.
hard hat: also hardhat, hard-hat, late 14c., "helmet;" 1935, "derby hat;" meaning "safety helmet" is from 1953; used figuratively for "construction worker" from 1970.
hard on (n.): "penile erection," 1893, from hard + on.
hard-bitten (adj.): "tough, tough in a fight," literally "given to hard biting," 1715, originally of dogs, from hard + bitten, with the past participle used actively (cf. ill-spoken).
hard-boiled (adj.): also hardboiled, 1723 in reference to eggs, from hard + boiled. In transferred sense "severe, tough," from 1886.
hard-headed (adj.): also hardheaded, 1580s, "stubborn," from hardhead "dull person" (1510s), from hard + head (n.). Meaning "practical" is attested from 1779.
hard-hearted (adj.): also hardhearted, "obdurate, unfeeling," late 12c. (implied in heard-heortnesse "hard-heartedness"); from hard + hearted. Sometimes in Middle English also meaning "bold, courageous" (15c.). Related: Hard-heartedly; hard-heartedness. Hard-heart "hard-hearted person" was in late Old English.
hard-line (adj.): 1958, originally in reference to Soviet communist policies, from hard + line (n.) in the political sense. Related: Hard-liner (1963).
hard-nosed (adj.): "stubborn," 1927, from hard + nose (n.). Earlier of bullets or shells with hard tips, and of dogs that had difficulty following a scent.
hard-wired (adj.): also hardwired, 1969, in computing; transferred to human brains from 1971; from hard + wired.
hard-working (adj.): also hardworking, 1774, from hard + working (see work).
hardback (n.): "type of book bound in stiff boards," 1954, from hard + back (n.).
hardball (n.): 1883 as the name of a game, from hard + ball (n.1). The figurative sense of "tough, uncompromising behavior" is from 1973.
hardcore: also hard-core; 1936 (n.); 1951 (adj.); from hard + core. Original use seems to be among economists and sociologists. Extension to pornography is attested by 1966. Also the name of a surfacing material.
harden (n.): c.1200 (replacing Old English heardian) "to make (something) hard," from hard + -en (1). Meaning "to become hard" is late 14c. Related: Hardened (figurative sense of "unfeeling" is from late 14c.); hardening.
hardener (n.): 1610s, from harden + -er (1).
hardly (adv.): c.1200, "in a hard manner, with great exertion or effort," from Old English heardlic "stern, severe, harsh; bold, warlike" (see hard + -ly (2)). Hence "assuredly, certainly" (early 14c.). Main modern sense of "barely, just" (1540s) reverses this, via the intermediate meaning "not easily, with trouble" (early 15c.). Formerly with superficial negative (not hardly).
hardness (n.): Old English heardnysse; see hard + -ness. Meaning "difficulty of action or accomplishment" is late 14c.
hardscrabble (adj.): 1804, U.S. colloquial, the name of an imaginary barren place "where a livelihood may be obtained only under great hardship and difficulty;" from hard + scrabble. First recorded in journals of Lewis and Clark. Perhaps the original notion is "vigorous effort made under great stress," though this sense is recorded slightly later (1812).
hardship (n.): c.1200, "quality of being hard," from hard + -ship. Meaning "disadvantage, suffering, privation" is c.1400.
hardtack (n.): 1836, "ship's biscuit," from hard (adj.) + tack (n.3); soft-tack was bread.
hardware (n.): mid-15c., "small metal goods," from hard + ware (n.). In the sense of "physical components of a computer" it dates from 1947. Hardware store attested by 1789.
hardwood (n.): 1560s, from hard + wood. From deciduous trees, distinguished from that of pines and firs.
hardy (adj.): c.1200, "bold, daring, fearless," from Old French hardi, from past participle of hardir "to harden, be or make bold," from Frankish *hardjan, from Proto-Germanic *hardjan "to make hard" (cf. Old Frisian herda, Old High German herten, Old Norse herða, Gothic gahardjan "make hard;" see hard). Sense influenced by English hard. Related: Hardily; hardiness. Hardhede "physical hardiness" is attested from early 15c.
hare (n.): Old English hara "hare," from West Germanic *hasan- (cf. Old Frisian hasa, Middle Dutch haese, Dutch haas, Old High German haso, German Hase), possibly with a sense of "gray" (cf. Old English hasu, Old High German hasan "gray"), from PIE *kas- "gray" (cf. Latin canus "white, gray, gray-haired"). Perhaps cognate with Sanskrit sasah, Afghan soe, Welsh ceinach "hare." Rabbits burrow in the ground; hares do not. Hare-lip is from 1560s.
þou hast a crokyd tunge heldyng wyth hownd and wyth hare. ["Jacob's Well," c.1440]