Online Etymology Dictionary

henceforth (adv.): late 14c., earlier henne forth (late Old English); see hence + forth.
henceforward (adv.): late 14c., from hence + forward (adv.).
henchman (n.): mid-14c., hengestman, later henshman (mid-15c.) "high-ranking servant (usually of gentle birth), attendant upon a king, nobleman, etc.," originally "groom," probably from man (n.) + Old English hengest "horse, stallion, gelding," from Proto-Germanic *hangistas (cf. Old Frisian hengst, Dutch hengest, German Hengst "stallion"), perhaps literally "best at springing," from PIE *kenku- (cf. Greek kekiein "to gush forth;" Lithuanian sokti "to jump, dance;" Breton kazek "a mare," literally "that which belongs to a stallion").

Perhaps modeled on Old Norse compound hesta-maðr "horse-boy, groom." The word became obsolete in England but was retained in Scottish as "personal attendant of a Highland chief," in which sense Scott revived it in literary English from 1810. Sense of "obedient or unscrupulous follower" is first recorded 1839, probably based on a misunderstanding of the word as used by Scott.
hendeca-: word-forming element meaning "eleven," from Latinized form of Greek hendeka "eleven," from hen, neuter of eis "one" + deka "ten" (see ten).
hendiadys (n.): 1580s, figure of speech in which two nouns joined by and are used in place of a noun and an adjective; from Medieval Latin alteration of Greek hen dia duoin "one (thing) by means of two." If this term was used by Greek grammarians it is no longer found in their writings, but it is frequent among Latin writers.
henge (n.): 1740, noted as a Yorkshire word for structures such as Stonehenge.
Henley: town on the Thames in Oxfordshire, site of annual regatta since 1839. The name is Old English hean-leage "(settlement) at or by the high wood."
henna (n.): c.1600, "dye or cosmetic from the henna plant," from Arabic hinna, name for the small thorny tree (Egyptian Privet, Lawsonia inermis), the leaves of which are used to make the reddish dye; said to be of Persian origin. Related: Hennaed (1860).
Hennessey: Irish surname, from O'(h)Aonghusa "descendant of Aonghus" ("one-choice").
henotheism (n.): 1860, from Greek henos, neuter of eis "one" (from PIE *sem- "one, as one") + theism. Devotion to a single god without asserting that he is the only god. Coined by (Friedrich) Max Müller (1823-1900), professor of comparative philology at Oxford. Related: Henotheist.
henpecked (adj.): 1670s, an image from hen + peck (v.).
The henpect Man rides behind his Wife, and lets her wear the Spurs and govern the Reins. [Samuel Butler]
The verb henpeck (1680s) apparently is a back-formation.
Henrietta: fem. proper name, from French Henriette, fem. diminutive of Henri (see Henry). In late 19c. a type of light dress fabric.
Henry: masc. proper name, from French Henri, from Late Latin Henricus, from German Heinrich, from Old High German Heimerich, literally "the ruler of the house," from heim "home" + rihhi "ruler." One of the most popular Norman names after the Conquest.
heortology (n.): "study of religious feasts and calendars," 1900, from Greek heorte "feast" + -ology. The immediate source of the English word is in French or German.
hep (1): "aware, up-to-date," first recorded 1908 in "Saturday Evening Post," but said to be underworld slang, of unknown origin. Variously said to have been the name of "a fabulous detective who operated in Cincinnati" [Louis E. Jackson and C.R. Hellyer, "A Vocabulary of Criminal Slang," 1914] or a saloonkeeper in Chicago who "never quite understood what was going on ... (but) thought he did" ["American Speech," XVI, 154/1]. Taken up by jazz musicians by 1915; hepcat "addict of swing music" is from 1938. With the rise of hip (adj.) by the 1950s, the use of hep ironically became a clue that the speaker was unaware and not up-to-date.
hep (2): cry of those leading pogroms or attacks on Jews in Europe, 1819 in reference to Jewish explusions by mobs in various German cities in that year (later called the hep-hep riots); perhaps originally the cry of a goatherd, or of a hunter urging on dogs, but popularly said at the time to be acronym of Latin Hierosolyma Est Perdita "Jerusalem is destroyed," which, as H.E.P., supposedly was emblazoned on the banners of medieval recruiters for the Crusades who drew mobs that subsequently turned on local Jewish populations. That such things happened is true enough, but the story about the supposed acronym sounds like folk etymology.
hepar (n.): metallic sulfide, 1690s, from Medieval Latin, from Greek hepar "liver" (see hepatitis); so called for its color.
heparin (n.): substance found in the liver, lungs and other tissues, 1918, from from Greek hepar "liver" (see hepatitis) + -in (2).
hepatic (adj.): late 14c., epatike, from Old French hepatique or directly from Latin hepaticus "pertaining to the liver," from Greek hepatikos, from hepar (genitive hepatos) "liver" (see hepatitis). As a noun, "medicine for the liver," from late 15c.
hepatitis (n.): 1727, coined from Greek hepatos, genitive of hepar "liver," from PIE root *yekwr- (cf. Sanskrit yakrt, Avestan yakar, Persian jigar, Latin jecur, Old Lithuanian jeknos "liver") + -itis "inflammation."
Hephaestus: Greek god of fire and metal-working, Roman spelling of Greek Hephaistos, a pre-Hellenic word of unknown origin.
Hephzibah: fem. proper name, biblical, from Hebrew Hephtzibah, literally "my delight is in her," from hephtzi "my delight" (from haphetz "to delight, to desire") + bah "in her."
Hepplewhite: as a modifier, by 1878, in reference to style of furniture introduced in England by cabinetmaker George Hepplewhite (d.1786). The proper name is from Heblethwaite, near Sedbergh in the West Riding of Yorkshire.
hepta-: before vowels hept-, word-forming element meaning "seven," from Greek hepta "seven" (see seven).
heptagon (n.): 1560s, from Middle French heptagon, from Greek heptagonon, from hepta "seven" (cognate with Latin septem, Gothic sibun, Old English seofon; see seven) + gonia "angle" (see knee). Related: Heptagonal.
her (objective case): Old English hire, third person singular feminine dative pronoun, which beginning in 10c. replaced accusative hie (see he). Cognate with Old Frisian hiri, Middle Dutch hore, Dutch haar, Old High German iru, German ihr.
her (possessive case): Old English hire, third person singular feminine genitive form of heo "she" (see she).
Hera: sister and wife of Zeus, from Greek Hera, literally "protectress," related to heros "hero," originally "defender, protector."
Heracles: also Herakles, alternate (more classically correct) forms of Hercules.
herald (n.): late 13c. (in Anglo-Latin); c.1200 as a surname, "messenger, envoy," from Anglo-French heraud, Old French heraut, hiraut (12c.), perhaps from Frankish *hariwald "commander of an army," from Proto-Germanic *harja "army" (from PIE root *koro- "war;" see harry) + *waldaz "to command, rule" (see wield). The form fits, but the sense evolution is difficult to explain, unless in reference to the chief officer of a tournament, who introduced knights and made decisions on rules (which was one of the early senses, often as heraud of armes, though not the earliest in English).
herald (v.): late 14c., "to sound the praises of," from herald (n.). Related: Heralded; heralding.
heraldic (adj.): 1772, on model of French héraldique (15c.), from Medieval Latin heraldus (see herald).
heraldry (n.): "art of arms and armorial bearings," late 14c., heraldy, from Old French hiraudie "heralds collectively," from hiraut (see herald (n.)). The spelling with -r- is attested from 1570s (cf. poetry, pedantry).
herb (n.): c.1300, erbe "non-woody plant," from Old French erbe "grass, herb, plant" (12c.), from Latin herba "grass, an herb, herbage, turf." Refashioned after Latin since 15c., but the h- was mute until 19c. Slang meaning "marijuana" is attested from 1960s.
herbaceous (adj.): 1640s, from Latin herbaceus, from herba (see herb).
herbage (n.): late 14c., "non-woody plants collectively," from Old French erbage or directly from Medieval Latin herbagium; see herb + -age.
herbal (adj.): 1610s, from Latin herbalis, from herba (see herb).
herbalist (n.): 1590s; see herbal + -ist. Earlier such a person might have been called herber (early 13c. as a surname).
Herbert: masc. proper name, introduced in England by the Normans, from Old French Herbert, Latinized from Frankish *Hari-berct, *Her(e)-bert, literally "army-bright."
herbicide (n.): 1888, originally a trademark name, from herb + -cide.
herbivore (n.): 1851, from Modern Latin herbivora (1830) or French herbivore (1748), from Latin herbivorus, from herba "a herb" + vorare "devour, swallow" (see voracity).
herbivorous (adj.): "plant-eating," 1660s, from Modern Latin herbivorus, from Latin herba "a herb" + vorare "devour, swallow" (see voracity).
Herculean (adj.): 1590s, from Hercules + -an.
Hercules: hero, son of Zeus and Alcmene, c.1200 (originally in reference to the Pillars of Hercules), also Ercules, from Latin Hercles, from Greek Herakles, literally "Glory of Hera;" from Hera (q.v.) + kleos "glory, renown" (see Clio). Used figuratively of strength since late 14c. Vocative form Hercule was a common Roman interjection (especially me Hercule!) "assuredly, certainly."
Hercynian (adj.): 1580s, designating the forest-covered mountains of ancient Germany, from Latin Hercynia (silva) "Hercynian (forest)," related to Greek Orkynios drymos, probably from Old Celtic *Perkunya, from PIE *perq(o)- "oak, oak forest, wooded mountain" (see fir).
herd (n.): Old English heord "herd, flock," from Proto-Germanic *herdo- (cf. Old Norse hjorð, Old High German herta, German Herde, Gothic hairda "herd"), from PIE *herdh- "a row, group" (cf. Sanskrit sardhah "herd, troop," Old Church Slavonic čreda "herd," Greek korthys "heap," Lithuanian kerdŽius "shepherd"). Herd instinct in psychology is first recorded 1908.
herd (v.): mid-13c., “to watch over or herd (livestock);” of animals, “to gather in a herd, to form a flock,” late 14c., from herd (n.). Related: Herded; herding.
herdsman (n.): Old English heordman, but the word was not common until herd (Old English hierde) in sense "keeper of domestic animals which go in herds" fell from use (cf. shepherd). See herd (n.) + man (n.). Intrusive -s- appeared early 15c., on model of craftsman, etc.
here: Old English her "in this place, where one puts himself," from Proto-Germanic pronomial stem *hi- (from PIE *ki- "this;" see he) + adverbial suffix -r. Cognate with Old Saxon her, Old Norse, Gothic her, Swedish här, Middle Dutch, Dutch hier, Old High German hiar, German hier.

Phrase here today and gone tomorrow first recorded 1680s in writings of Aphra Behn. Here's to _____ as a toast is from 1590s, probably short for here's health to _____. In vulgar speech, this here as an adjective is attested from 1762. To be neither here nor there "of no consequence" attested from 1580s. Here we go again as a sort of verbal roll of the eyes is attested from 1950. Noun phrase here and now "this present life" is from 1829.
hereabout: "about this, with regard to this matter," c.1200, from here + about. Meaning "in the vicinity, near here" is from early 13c. Hereabouts is from 1590s.