"a stew of meat cut into small pieces," 1660s, from hash (v.). Meaning "a mix, a mess" is from 1735. Cryptographic use in computing is by 1979.
1650s, "to hack, chop into small pieces," from French hacher "chop up" (14c.), from Old French hache "ax" (see hatchet). Hash browns (1926) is short for hashed browned potatoes (1886), with the -ed omitted, as in mash potatoes. The hash marks on a football field were so called by 1954, from their similarity to hash marks, armed forces slang for "service stripes on the sleeve of a military uniform" (1909), which supposedly were called that because they mark the number of years one has had free food (that is, hash (n.1)) from the Army; but perhaps there is a connection with the noun form of hatch (v.2).
Jewish new year, 1846, from Hebrew rosh hashshanah, literally "head of the year," from rosh "head of" + hash-shanah "the year."
"a medley, hash, hodge-podge," 1550s, from French galimafrée "hash, ragout, dish made of odds and ends," from Old French galimafree, calimafree "sauce made of mustard, ginger, and vinegar; a stew of carp" (14c.), which is of unknown origin. Perhaps from Old French galer "to make merry, live well" (see gallant) + Old North French mafrer "to eat much," from Middle Dutch maffelen [Klein]. Weekley sees in the second element the proper name Maufré. Hence, figuratively, "any inconsistent or absurd medley."
"a mixture of various kinds; a medley; a combination of diverse objects, parts, or elements," 1590s, from Latin miscellanea "a writing on miscellaneous subjects," originally "meat hash, hodge-podge" (food for gladiators), neuter plural of miscellaneus "mixed," from miscere "to mix" (from PIE root *meik- "to mix"). From 1610s as "a diversified literary collection;" 1630s as "a book containing compositions on various subjects" (miscellanea in this sense is from 1570s).
also hasheesh, 1590s, from Arabic hashīsh "powdered hemp, hemp," extended from sense "herbage, dry herb, rough grass, hay."
Its earliest record as a nickname for cannabis drug is in 13th century Arabic. Its earliest in English is in a traveller's report from Egypt in 1598. It is rare in English until the 19th century. The wordform in English today dates from the early 19th century. The word entered all the bigger Western European languages in the early to mid 19th century if you don't count occasional mentions in travellers' reports before then. ["English Words of Arabic Ancestry"]
"machine to measure and indicate time mechanically" (since late 1940s also electronically), late 14c., clokke, originally "clock with bells," probably from Middle Dutch clocke (Dutch klok) "a clock," from Old North French cloque (Old French cloke, Modern French cloche "a bell"), from Medieval Latin clocca "bell," which probably is from Celtic (compare Old Irish clocc, Welsh cloch, Manx clagg "a bell") and spread by Irish missionaries (unless the Celtic words are from Latin). Ultimately of imitative origin.
Wherever it actually arose, it was prob. echoic, imitating the rattling made by the early handbells of sheet-iron and quadrilateral shape, rather than the ringing of the cast circular bells of later date. [OED]
Replaced Old English dægmæl, from dæg "day" + mæl "measure, mark" (see meal (n.1)). The Latin word was horologium (source of French horologe, Spanish reloj, Italian oriolo, orologio); the Greeks used a water-clock (klepsydra, literally "water thief;" see clepsydra).
The image of put (or set) the clock back "return to an earlier state or system" is from 1862. Round-the-clock (adj.) is from 1943, originally in reference to air raids. To have a face that would stop a clock "be very ugly" is from 1886. (Variations from c. 1890 include break a mirror, kill chickens.)
I remember I remember
That boarding house forlorn,
The little window where the smell
Of hash came in the morn.
I mind the broken looking-glass,
The mattress like a rock,
The servant-girl from County Clare,
Whose face would stop a clock.
[... etc.; The Insurance Journal, January 1886]