hand (n.)youdaoicibaDictYouDict
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 (cognates: 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 The original Old English plural handa was superseded in Middle English by handen, later hands.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, represented by Latin manus (see manual (adj.)) is represented in Old English by mund "hand," but more usually "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. 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]
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 is from c. 1500. Hand-in-hand attested from c. 1500 as "with hands clasped;" figurative sense of "concurrently" recorded from 1570s.
retail (n.)youdaoicibaDictYouDict
early 15c., "sale of commodities in small quantities or parcels or at second hand" (opposed to wholesale), from Old French retail "piece cut off, shred, scrap, paring" (Modern French retaille), from retaillier (see retail (v.)). The notion of the English word is "a selling by the piece." This sense is not in French, however, and comes perhaps from cognate Italian ritaglio, which does have that sense. As an adjective, "of or pertaining to sale at retail," c. 1600.
second (n.1)youdaoicibaDictYouDict
"one-sixtieth of a minute of degree," also "sixtieth part of a minute of time," late 14c. in geometry, from Old French seconde, from Medieval Latin secunda, short for secunda pars minuta "second diminished part," the result of the second division of the hour by sixty (the first being the "prime minute," now called the minute), from Latin secunda, fem. of secundus (see second (adj.)). The second hand of a clock is attested from 1759.
split-second (n.)youdaoicibaDictYouDict
1884, originally the name of a type of stopwatch with two second hands that could be stopped independently. Meaning "a fraction of a second" is from 1912, from split (adj.) + second (n.1); adjectival meaning "occurring in a fraction of a second" is from 1946.