Middle English kēpen, from late Old English cepan (past tense cepte) "to seize, hold; seek after, desire," also "to observe or carry out in practice; look out for, regard, pay attention to," from Proto-Germanic *kopjan, which is of uncertain origin. Old English cepan was used c. 1000 to render Latin observare, so perhaps it is related to Old English capian "to look" (from Proto-Germanic *kap-), which would make the basic sense "to keep an eye on, see to it."
The word prob. belonged primarily to the vulgar and non-literary stratum of the language; but it comes up suddenly into literary use c. 1000, and that in many senses, indicating considerable previous development. [OED]
The senses exploded in Middle English: "to guard, defend" (12c.); "restrain (someone) from doing something" (early 13c.); "take care of, look after; protect or preserve (someone or something) from harm, damage, etc." (mid-13c.); "preserve, maintain, carry on" a shop, store, etc. (mid-14c.); "prevent from entering or leaving, force to remain or stay" (late 14c.); "preserve (something) without loss or change," also "not divulge" a secret, private information, etc., also "to last without spoiling" (late 14c.); "continue on" (a course, road, etc.), "adhere to" a course of action (late 14c.); "stay or remain" (early 15c.); "to continue" (doing something) (mid-15c.). It is used to translate both Latin conservare "preserve, keep safe" and tenere "to keep, retain."
From 1540s as "maintain for ready use;" 1706 as "have habitually in stock for sale." Meaning "financially support and privately control" (usually in reference to mistresses) is from 1540s; meaning "maintain in proper order" (of books, accounts) is from 1550s.
To keep at "work persistently" is from 1825; to keep on "continue, persist" is from 1580s. To keep up is from 1630s as "continue alongside, proceed in pace with," 1660s as "maintain in good order or condition, retain, preserve," 1680s as "support, hold in an existing state." To keep it up "continue (something) vigorously" is from 1752. To keep to "restrict (oneself) to" is from 1711. To keep off (trans.) "hinder from approach or attack" is from 1540s; to keep out (trans.) "prevent from entering" is from early 15c.
"man who draws attention by unusual finery of dress and fastidiousness manners, a fop," c. 1780, of uncertain origin; attested earliest in a Scottish border ballad:
I've heard my granny crack
O' sixty twa years back
When there were sic a stock of Dandies O
etc. In that region, Dandy is diminutive of Andrew (as it was in Middle English generally). OED notes that the word was in vogue in London c. 1813-1819. His female counterpart was a dandizette (1821) with French-type ending.
Meaning "anything superlative or fine" is from 1786. As an adjective, "characteristic of a dandy, affectedly neat and trim," by 1813; earlier in the sense of "fine, splendid, first-rate" (1792) and in this sense it was very popular c. 1880-1900.
The popular guess, since at least 1827, is that it is from French Dandin, a mock surname for a foolish person used in 16c. by Rabelais (Perrin Dandin), also by Racine, La Fontaine, and Molière, from dandiner "to walk awkwardly, waddle." Farmer rejects this and derives it from dandyprat, an Elizabethan word for "a dwarf; a page; a young or insignificant person," originally (early 16c.) the name of a small silver coin. Both words are of unknown origin, and OED finds the connection of both to dandy to be "without any apparent ground." English dandy was itself borrowed into French c. 1830.
Jack-a-Dandy, or Jack O'Dandy figures in writings from the early 17c. He is listed among other famous Jacks in "Iack a Lent" (1620) and is sometimes defined as an impertinent little man, but other uses are unclear as to sense and in at least one instance from 1620s he is a bogeyman character.
DANDY was first applied half in admiration half in derision to a fop about the year 1816. John Bee (Slang Dict., 1823) says that Lord Petersham was the chief of these successors to the departed Macaronis, and gives, as their peculiarities, 'French gait, lispings, wrinkled foreheads, killing king's English, wearing immense plaited pantaloons, coat cut away, small waistcoat, cravat and chitterlings immense, hat small, hair frizzled and protruding.' [Farmer and Henley, "Slang and its Analogues," 1891]
a Middle English merger of Old English line "cable, rope; series, row, row of letters; rule, direction," and Old French ligne "guideline, cord, string; lineage, descent" (12c.), both from Latin linea "linen thread, string, plumb-line," also "a mark, bound, limit, goal; line of descent," short for linea restis "linen cord," and similar phrases, from fem. of lineus (adj.) "of linen," from linum "linen" (see linen).
The earliest sense in Middle English was "cord used by builders for taking measurements;" extended late 14c. to "a thread-like mark" (from sense "cord used by builders for making things level," mid-14c.), also "track, course, direction." Meaning "limit, boundary" (of a county, etc.) is from 1590s. The mathematical sense of "length without breadth" is from 1550s. From 1530s as "a crease of the face or palm of the hand." From 1580s as "the equator."
Sense of "things or people arranged in a straight line" is from 1550s. Now considered American English, where British English uses queue (n.), but the sense appears earliest in English writers. Sense of "chronologically continuous series of persons" (a line of kings, etc.) is from late 14c.
Meaning "one's occupation, branch of business" is from 1630s, according to OED probably from misunderstood KJV translation of II Corinthians x.16, "And not to boast in another mans line of things made ready to our hand," where line translates Greek kanon which probably meant "boundary, limit;" the phrase "in another man's line" being parenthetical.
Commercial meaning "class of goods in stock" is from 1930, so called from being goods received by the merchant on a line in the specific sense "order given to an agent" for particular goods (1834). Insurance underwriting sense is from 1899. Line of credit is from 1958.
Meaning "series of public conveyances" (coaches, later ships) is from 1786; meaning "continuous part of a railroad" is from 1825. Meaning "telegraph wire between stations" is from 1847 (later "telephone wire"). Meaning "cord bearing hooks used in fishing" is from c. 1300. Meaning "policy or set of policies of a political faction" is 1892, American English, from notion of a procession of followers; this is the sense in the political party line, and, deteriorated, it is the slang line that means "glib and plausible talk meant to deceive."
In British army, the Line (1802) is the regular, numbered troops, as distinguished from guards, auxiliaries, militia, etc. In the Navy (1704) it refers to the battle line (the sense in ship of the line, which is attested from 1706).
Dutch lijn, Old High German lina, German Leine, Old Norse lina "a cord, rope," are likewise from Latin. Spanish and Italian have the word in the learned form linea. In continental measurements, a subdivision of an inch (one-tenth or one-twelfth in England), attested in English from 1660s but never common. Also see lines.
To get a line on "acquire information about" is from 1903. To lay it on the line is from 1929 as "to pay money;" by 1954 as "speak plainly." End of the line "as far as one can go" is from 1948. One's line of work, meaning "pursuit, interest" is from 1957, earlier line of country (1861). Line-drawing is from 1891. A line-storm (1850) is a type supposed to happen in the 10 days or two weeks around the times the sun crosses the equator.
c. 1300, "to make, with an edged tool or instrument, an incision in; make incisions for the purpose of dividing into two or more parts; remove by means of a cutting instrument;" of an implement, "have a cutting edge," according to Middle English Compendium from a presumed Old English *cyttan, "since ME has the normal regional variants of the vowel." Others suggest a possible Scandinavian etymology from North Germanic *kut- (source also of Swedish dialectal kuta "to cut," kuta "knife," Old Norse kuti "knife"), or that it is from Old French couteau "knife."
From early 14c. as "to make or fashion by cutting or carving." From c. 1400 as "to intersect or cross." From early 15c. as "abridge or shorten by omitting a part."
Meaning "to wound the sensibilities of" is from 1580s (to cut the heart in the same sense is attested from early 14c.). Sense of "sever connection or relations with" is from 1630s.
Meaning "to be absent without excuse" is British university slang from 1794. Colloquial or slang sense of "move off with directness and rapidity" is from 1580s. Meaning "divide (a deck of cards) at random into parts before the deal" to prevent cheating is from 1530s.
Meaning "to dilute, adulterate" (liquor, etc.) is by 1930. Colloquial sense of "to divide or share" is by 1928, perhaps an image from meat-carving at table. As a director's call to halt recording or performing, by 1931 (in an article about Pete, the bulldog with the black-ringed eye in the Hal Roach studios shorts, who was said to know the word). The sense of "perform, execute" (c. 1600) is in cut capers "frisk about;" cut a dash "make a display."
To cut down is from late 14c. as "to fell;" by 1821 as "to slay" (as with a sword); 1857 as "to curtail." To cut (someone or something) down to size is from 1821 as "reduce to suitable dimensions;" the figurative sense, "reduce to the proper level of importance," is by 1927.
To cut in "enter suddenly and unceremoniously" is from 1610s; sense of "suddenly join in conversation, interrupt" is by 1830. To cut up "cut in pieces" is from 1570s. To cut back is from 1871 as "prune by cutting off shoots," 1913 in cinematography, "return to a previous scene by repeating a part of it," 1943 as "reduce, decrease" (of expenditures, etc.). To cut (something) short "abridge, curtail, interrupt" is from 1540s.
In nautical use to cut a feather (1620s) is to move so fast as to make water foam under the bow. To cut and run (1704) also is originally nautical, "cut cable and set sail immediately," as in an emergency, hence, generally, "to make off suddenly."
To cut the teeth "have the teeth grow through the gums" as an infant is from 1670s. To cut both ways in the figurative sense of "have a good and bad effect" is from c. 1600. To cut loose "set (something) free" is by 1828; intransitive sense "begin to act freely" is by 1909.
Cut it out "remove (something) by or as if by cutting" yielded a figurative use in the command cut it out! "Stop! That's enough!" by 1933. The evolution seems to have begun earlier. A piece attributed to the Chicago Live Stock World that made the rounds in trade publications 1901-02 begins:
When you get 'hot' about something and vow you are going to rip something or somebody up the back—cut it out.
If you feel disposed to try the plan of building yourself up by tearing some one else down—cut it out.
Playing on both senses, it ends with "Should you, after reading this preachy stuff, fear you might forget some of the good advice—cut it out."