Old English hond, hand "the human hand;" also "side, part, direction" (in defining position, to either right or left); also "power, control, possession" (on the notion of the hand's grip or hold), from Proto-Germanic *handuz (source also of Old Saxon, Old Frisian, Dutch, German hand, Old Norse hönd, Gothic handus), which is of uncertain origin.
The original Old English plural handa was superseded in Middle English by handen, later hands. Indo-European "hand" words tend to be from roots meaning "seize, take, collect" or are extended from words originally meaning only a part of the hand (such as Irish lam, Welsh llaw, cognate with Latin palma and originally meaning "palm of the hand"). One ancient root (*man- (2)), represented by Latin manus is the source of Old English mund "hand," but more usually meaning "protection, guardianship; a protector, guardian."
Meaning "manual worker, person who does something with his hands" is from 1580s, hence "hired workman" (1630s) and "sailor in a ship's crew" (1660s). Meaning "agency, part in doing something" is from 1590s. Clock and watch sense is from 1570s. Meaning "round of applause" is from 1838. The linear measure of 4 inches (originally 3) is from 1560s, now used only in giving the height of horses. The meaning "playing cards held in one player's hand" is from 1620s; that of "a round at a card game" is from 1620s. Meaning "handwriting" is from late 14c.; also "one's style of penmanship" (early 15c.). The word in reference to the various uses of hands in making a pledge is by c. 1200; specifically "one's pledge of marriage" by late 14c.
First hand, second hand, etc. (mid-15c.) are from the notion of something being passed from hand to hand. At hand is from c. 1200 as "near in time," c. 1300 as "within reach." Out of hand (1590s) is opposite of in hand "under control" (c. 1200). Adverbial phrase hand-over-fist (1803) is nautical, suggestive of hauling or climbing by passing the hands one before the other alternately.
Phrase on the one hand ... on the other hand is recorded from 1630s, a figurative use of the physical sense of hand in reference to position on one side or the other side of the body (as in the lefthand side), which goes back to Old English Hands up! as a command from a policeman, robber, etc., is from 1863, from the image of holding up one's hands as a token of submission or non-resistance. Hand-to-hand "in close contact," of fighting, is from c. 1400. Hand-to-mouth "said of a person who spends his money as fast as he gets it, who earns just enough to live on from day to day" [Bartlett] is from c. 1500. Hand-in-hand attested from c. 1500 as "with hands clasped;" figurative sense of "concurrently" recorded from 1570s.
late 14c., of language, "German, non-Scandinavian continental Germanic," also as a noun, "a German language;" also in Duche-lond "Germany." By mid-15c. distinguished into Higher and Lower, and used after c. 1600 in the narrower sense "Hollanders, residents of the Netherlands." From Middle Dutch duutsch, from Old High German duitisc, from Proto-Germanic *theudō "popular, national" (source of Modern German Deutsch), from PIE *teuta- "tribe" (compare Teutonic).
It corresponds to the Old English adjective þeodisc "belonging to the people," which was used especially of the common language of Germanic people (as opposed to Latin), a derivative of the Old English noun þeod "people, race, nation." The language name is first attested in Latin as theodice (786 C.E.) in correspondence between Charlemagne's court and the Pope, in reference to a synodical conference in Mercia; thus it refers to Old English. Its first use in reference to a German language (as opposed to a Germanic one) is two years later. The sense was extended from the language to the people who spoke it (in German, Diutisklant, ancestor of Deutschland, was in use by 13c.).
The sense in of the adjective in English narrowed to "of the Netherlands" in 17c., after they became a united, independent state and the focus of English attention and rivalry. In Holland, Duits (formerly duitsch) is used of the people of Germany. The old use of Dutch for "German" continued in America (Irving and Cooper still distinguish High Dutch "German" and Low Dutch "Dutch") and survives in Pennsylvania Dutch for the descendants of religious sects that immigrated from the Rhineland and Switzerland and their language.
Since c. 1600, Dutch (adj.) has been a "pejorative label pinned by English speakers on almost anything they regard as inferior, irregular, or contrary to 'normal' (i.e., their own) practice" [Rawson]. E.g. ironical Dutch treat, of each person paying for himself (1887), Dutch courage "boldness inspired by intoxicating spirits" (1809), nautical Dutch talent "any piece of work not done in shipshape style (1867), etc. -- probably exceeded in such usage only by Indian and Irish -- reflecting first British commercial and military rivalry and later heavy German immigration to U.S.
Dutch concert, a concert in which each one sings his own song at the same time that his neighbor sings his; or a concert in which each one sings a verse of any song he pleases, some well-known chorus being sung after each verse. [Century Dictionary, 1897]
The Dutch themselves spoke English well enough to understand the unsavory connotations of the label and in 1934 Dutch officials were ordered by their government to stop using the term Dutch. Instead, they were to rewrite their sentences so as to employ the official The Netherlands. [Rawson]
Dutch oven is from 1769; OED lists it among the words describing things from Holland, but perhaps it is here used in the slighting sense. Dutch elm disease (1927) so called because it was first discovered in Holland (caused by fungus Ceratocystis ulmi). A Dutch uncle (1838) is one who is kindly severe and direct.