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.
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"  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.
"an inexpressible something," French, literally "I do not know what."
[T]hey are troubled with the je-ne-scay-quoy, that faign themselves sick out of niceness but know not where their own grief lies, or what ayls them. [Thomas Blount, "Glossographia," 1656]
to win something hands down (1855) is from horse racing, from a jockey's gesture of letting the reins go loose in an easy victory.
The Two Thousand Guinea Stakes was not the best contested one that it has been our fortune to assist at. ... [T]hey were won by Meteor, with Scott for his rider; who went by the post with his hands down, the easiest of all easy half-lengths. Wiseacre certainly did the best in his power to spoil his position, and Misdeal was at one time a little vexatious. [The Sportsman, report from April 26, 1840]
Ancient Greek had akoniti "without a struggle, easily," from akonitos (adj.), literally "without dust," specifically "without the dust of the arena."
"grass mown," Old English heg (Anglian), hieg, hig (West Saxon) "grass cut or mown for fodder," from Proto-Germanic *haujam (source also of Old Norse hey, Old Frisian ha, Middle Dutch hoy, German Heu, Gothic hawi "hay"), literally "that which is cut," or "that which can be mowed" (from PIE *kau- "to hew, strike;" source also of Old English heawan "to cut;" see hew).
Slang phrase hit the hay (pre-1880) was originally "to sleep in a barn;" hay in the general figurative sense of "bedding" is from 1903; roll in the hay (n.) is from 1941.
1797, "crape-like fabric," especially white or colored, not the ordinary black for mourning, from French crêpe, Old French crespe "ruff, ruffle, frill" (14c.), from Latin crispa, fem. of crispus "curled, wrinkled, having curly hair," from PIE root *sker- (2) "to turn, bend." Crepe paper is attested by 1895.
Meaning "small, thin pancake" is from 1877, from French galette crêpe "curled/wrinkled pancake" (compare crumpet). Recipes for what seem to be similar things are in English cookery books from late 14c., often as crispes, cryspes, but at least once as cryppys. Related: Creperie. Crepe suzette "light pancake served rolled or folded, sprinkled with orange liqueur or brandy and flambéed," is by 1910 in English (suzette pancake is from 1907) and was the usual form until c. 1980.
Contemporary evidence suggests that its most likely creator was a head waiter at Restaurant Paillard in Paris in 1889, and that it was named in honour of an actress in the Comédie Française who played the part of a maid serving pancakes. ... [T]hey were for perhaps the first two thirds of the twentieth century the epitome of the luxurious, expensive, and exclusive dessert. [Ayto, "Diner's Dictionary"]
large, long-tailed, stalk-eyed, 10-legged marine shellfish (Homarus vulgaris), early Middle English lopster, lopister, from Old English loppestre "lobster," also "locust," a corruption of Latin locusta, lucusta "marine shellfish, lobster;" also "locust, grasshopper," which is of unknown origin. De Vaan writes that "The only word similar in form and meaning is lacerta 'lizard; mackerel', but there is no common preform in sight. ... [T]hey could be cognate words in the language from which Latin borrowed these forms."
The change of Latin -c- to English -p- (and, from late 14c., to -b-) is unexplained; perhaps it is by influence of Old English loppe, lobbe "spider." The ending seems to have been altered by the old fem. agent noun suffix (preserved in Baxter, Webster, etc.; see -ster), which approximated the sound of Latin -sta.
OED says the Latin word originally meant "lobster or some similar crustacean, the application to the locust being suggested by the resemblance in shape." Trilobite fossils in Worcestershire limestone quarries were known colloquially as locusts, which seems to have been the generic word for "unidentified arthropod" (as apple was for "foreign fruit"). Locusta in the sense "lobster" also appears in Old Cornish legast and French langouste (12c.), now "crawfish, crayfish," but in Old French both "lobster" and "locust" (a 13c. psalter has God giving over the crops of Egypt to the langoustes).
As slang for "a British soldier" since 1640s, originally in reference to the jointed armor of the Roundhead cuirassiers, later (1660) to the red coat, the color of a boiled lobster.
Sir William Waller having received from London [in June 1643] a fresh regiment of five hundred horse, under the command of sir Arthur Haslerigge, which were so prodigiously armed that they were called by the other side the regiment of lobsters, because of their bright iron shells with which they were covered, being perfect curasseers. [Lord Clarendon, "History of the Rebellion," 1647]