Online Etymology Dictionary

mot (n.): "a witty saying," 1580s, from French mot (12c.) "remark, short speech," literally "word," cognate of Italian motto, from Latin mutum "grunt, murmur" (see mutter). Mot juste (1912) is French, literally "exact word," the precisely appropriate expression in some situation.
The mot juste is an expression which readers would like to buy of writers who use it, as one buys one's neighbour's bantam cock for the sake of hearing its voice no more. [Fowler]
hair-trigger (n.): 1795; Figurative use by 1841. Hair perhaps in reference to the slight pressure required to activate it.
The difference between a hair-trigger and a common trigger is this--the hair-trigger, when set, lets off the cock by the slightest touch, whereas the common trigger requires a considerable degree of force, and consequently is longer in its operation. [Charles James, "Military Dictionary," London, 1802]
gallium (n.): metalic element that melts in the hand, discovered by spectral lines in 1875 by French chemist Lecoq de Boisbaudran (1838-1912), who named it apparently in honor of his homeland (see Gallic), but it has been suggested that he also punned on his own name (compare Latin gallus "cock," for which see gallinaceous). With metallic element ending -ium.
horologer (n.): late 14c., "clock-maker," via Latin from Greek horologe "clock, timepiece, instrument for measuring the hours of a day," from horologos "telling the hour," from hora "hour" (see hour) on model of astrologer, etc. Hence also obsolete English horologe "timepiece, sundial, hourglass, clock, cock" (late 14c.) and the old expression the devil in the horologe for "mischief in an orderly system" (17c.).
hackle (n.): Old English hacele "coat, cloak, vestment, mantle" (cognate with Old High German hachul, Gothic hakuls "cloak;" Old Norse hekla "hooded frock"), of uncertain origin. The same word with a sense of "bird plumage" is first recorded early 15c., though this might be from unrelated Middle English hackle "flax comb" (see heckle (n.)) on supposed resemblance of comb to ruffled feathers, or from an unrecorded continental Germanic word. Metaphoric extension found in phrases such as raise (one's) hackles (as a cock does when angry) is by 1881.
spar (v): late 14c., "go quickly, rush, dart, spring;" c. 1400, "to strike or thrust," perhaps from Middle French esparer "to kick" (Modern French éparer), from Italian sparare "to fling," from Latin ex- (see ex-) + parare "make ready, prepare," hence "ward off, parry" (see pare). Etymologists consider a connection with spur unlikely. Used in 17c. in reference to preliminary actions in a cock fight; figurative sense of "to dispute, bandy with words" is from 1690s. Extension to humans, in a literal sense, with meaning "to engage in or practice boxing" is attested from 1755. Related: Sparred; sparring.
hen (n.): Old English henn "hen," from West Germanic *hannjo (source also of Old Frisian henn, Middle Dutch henne, Old High German henna), fem. of *han(e)ni "male fowl, cock" (source of Old English hana "cock"), literally "bird who sings (for sunrise)," from PIE root *kan- "to sing" (see chant).

The original masculine word survives in German (Hahn "cock"), Swedish, Danish, etc. German also has a generic form, Huhn, for either gender of the bird. Extension to "female of any bird species" is early 14c. in English. Hen as slang for "woman" dates from 1620s; hence hen party "gathering of women," first recorded 1887. To be mad as a wet hen is from 1823, but the figure was used to indicate other states:
Some, on the contrary, are viciously opposite to these, who act so tamely and so coldly, that when they ought to be angry, to thunder and lighten, as one may say, they are no fuller of Heat, than a wet Hen, as the Saying is; .... ["Life of Mr. Thomas Betterton," London, 1710]

Orth. Out upon you for a dastardly Fellow; you han't the Courage of a wet Hen. ["A Sermon Preached at St. Mary-le-Bow, March 27, 1704"]
As wanton as a wet hen is in "Scots Proverbs" (1813). Among Middle English proverbial expressions was nice as a nonne hen "over-refined, fastidiously wanton" (c. 1500); to singen so hen in snowe "sing miserably," literally "sing like a hen in snow" (c. 1200). The figure of the hen with one chick dates to 1590s. Hen's teeth as a figure of scarceness is attested by 1838.
call (v.): Old English ceallian "to call, shout," less common than clipian; replaced by related Old Norse kalla "to cry loudly," from Proto-Germanic *kall- (source also of Dutch kallen "to talk," Old High German kallon "to call"), from PIE root *gal- (2) "to call, scream, shriek, shout" (source also of Sanskrit garhati "bewail, criticize;" Latin gallus "cock;" Old High German klaga, German Klage "complaint, grievance, lament, accusation;" Old English clacu "affront;" Old Church Slavonic glasu "voice," glagolu "word;" Welsh galw "call"). Related: Called; calling.

Meaning "to give a name to" is mid-13c. Coin-toss sense is from 1801. Meaning "to visit" (Middle English) was literally "to stand at the door and call." Telephone/telegraph sense is from 1889. To call out someone to fight (1823) corresponds to French provoquer. To call it a day is from 1834.
fuss (n.): "trifling bustle," 1701, originally colloquial, perhaps an alteration of force (n.), or "echoic of the sound of something sputtering or bubbling" [OED], or from Danish fjas "foolery, nonsense." First attested in Anglo-Irish writers, but there are no obvious connections to words in Irish. To make a fuss was earlier to keep a fuss (1726). Fuss and feathers "bustle and display" is from 1848, American English, suggestive of a game cock or a peacock, originally of U.S. Army Gen. Winfield Scott (1786-1866) in the Mexican war.
Gen. Scott is said to be as particular in matters of etiquette and dress as Gen. Taylor is careless. The soldiers call one "Old Rough and Ready," and the other "Old Fuss and Feathers." ["The Mammoth," Nov. 15, 1848].
spur (n.): Old English spura, spora "metal implement worn on the heel to goad a horse" (related to spurnan "to kick"), from Proto-Germanic *spuron (source also of Old Norse spori, Middle Dutch spore, Dutch spoor, Old High German sporo, German Sporn "spur"), from PIE *spere- "ankle" (see spurn). Related to Dutch spoor, Old English spor "track, footprint, trace."

Generalized sense of "anything that urges on, stimulus," is from late 14c. As a sharp projection on the leg of a cock, from 1540s. Meaning "a ridge projecting off a mountain mass" is recorded from 1650s. Of railway lines from 1837. "Widely extended senses ... are characteristic of a horsey race" [Weekley]. Expression on the spur of the moment (1801) preserves archaic phrase on the spur "in great haste" (1520s). To win one's spurs is to gain knighthood by some valorous act, gilded spurs being the distinctive mark of a knight.
pimp (n.): c. 1600, of unknown origin, perhaps from Middle French pimpant "alluring in dress, seductive," present participle of pimper "to dress elegantly" (16c.), from Old French pimpelorer, pipelorer "decorate, color, beautify." Weekley suggests Middle French pimpreneau, defined in Cotgrave [French-English Dictionary, 1611] as "a knave, rascall, varlet, scoundrell," but Liberman is against this.
Judging by such recorded meanings of pimp as 'helper in mines; servant in logging camps,' this word was originally applied to boys and servants. [Liberman]
The word also means "informer, stool pigeon" in Australia and New Zealand and in South Africa, where by early 1960s it existed in Swahili form impimpsi. Pimpmobile first recorded 1973 (six years before Popemobile).
PIMP. A male procurer, or cock bawd; also a small faggot used about London for lighting fires, named from introducing the fire to the coals. [Grose, "Dictionary of the Vulgar Tongue," London, 1785]
reck (v.): Old English reccan (2) "take care of, be interested in, care for; have regard to, take heed of; to care, heed; desire (to do something)" (strong verb, past tense rohte, past participle rought), from West Germanic *rokjan, from Proto-Germanic *rokja- (source also of Old Saxon rokjan, Middle Dutch roeken, Old Norse rækja "to care for," Old High German giruochan "to care for, have regard to," German geruhen "to deign," which is influenced by ruhen "to rest").
And in that very moment, away behind in some courtyard of the City, a cock crowed. Shrill and clear he crowed, recking nothing of wizardry or war, welcoming only the morning that in the sky far above the shadows of death was coming with the dawn. [J.R.R. Tolkien, "Return of the King," 1955]
The -k- sound is probably a northern influence from Norse. No known cognates outside Germanic. "From its earliest appearance in Eng., reck is almost exclusively employed in negative or interrogative clauses" [OED]. Related: Recked; recking.
half: Old English half, halb (Mercian), healf (W. Saxon) "side, part," not necessarily of equal division (original sense preserved in behalf), from Proto-Germanic *halbaz "something divided" (source also of Old Saxon halba, Old Norse halfr, Old Frisian, Middle Dutch half, German halb, Gothic halbs "half"), perhaps from PIE (s)kel- (1) "to cut" (see shell (n.)). Noun, adjective, and adverb all were in Old English.

Used also in Old English phrases, as in modern German, to mean "one half unit less than," for example þridda healf "two and a half," literally "half third." The construction in two and a half, etc., is first recorded c. 1200. Of time, in half past ten, etc., first attested 1750; in Scottish, the half often is prefixed to the following hour (as in German, halb elf = "ten thirty"). To go off half-cocked in the figurative sense "speak or act too hastily" (1833) is in allusion to firearms going off prematurely; half-cocked in a literal sense "with the cock lifted to the first catch, at which position the trigger does not act" is recorded by 1750. In 1770 it was noted as a synonym for "drunk."
felon (n.): c. 1300, "one who deceives or commits treason; one who is wicked or evil; evil-doer," used of Lucifer and Herod, from Old French felon "evil-doer, scoundrel, traitor, rebel, oath-breaker, the Devil" (9c.), from Medieval Latin fellonem (nominative fello) "evil-doer," which is of uncertain origin, perhaps from Frankish *fillo, *filljo "person who whips or beats, scourger" (source of Old High German fillen "to whip"); or from Latin fel "gall, poison," on the notion of "one full of bitterness." Celtic origins also have been proposed.

Another theory (advanced by Professor R. Atkinson of Dublin) traces it to Latin fellare "to suck" (see fecund), which had an obscene secondary meaning in classical Latin (well-known to readers of Martial and Catullus), which would make a felon etymologically a "cock-sucker." OED inclines toward the "gall" explanation, but finds Atkinson's "most plausible" of the others.

Also by c. 1300 in English in a general legal sense "criminal; one who has committed a felony," however that was defined. Century Dictionary notes, "the term is not applicable after legal punishment has been completed." In Middle English it also was an adjective, "traitorous, wicked, malignant." Australian official James Mudie (1837), coined felonry "as the appellative of an order or class of persons in New South Wales,--an order which happily exists in no other country in the world."
horn (n.): Old English horn "horn of an animal; projection, pinnacle," also "wind instrument" (originally one made from animal horns), from Proto-Germanic *hurnaz (source also of German Horn, Dutch horen, Old Frisian horn, Gothic haurn), from PIE *ker- (1) "horn; head, uppermost part of the body," with derivatives refering to horned animals, horn-shaped objects and projecting parts (source also of Greek karnon "horn," Latin cornu "horn," Sanskrit srngam "horn," Persian sar "head," Avestan sarah- "head," Greek koryphe "head," Latin cervus "deer," Welsh carw "deer").

Late 14c. as "one of the tips of the crescent moon." The name was retained for a class of musical instruments that developed from the hunting horn; the French horn is the true representative of the class. Of dilemmas from 1540s; of automobile warning signals from 1901. Slang meaning "erect penis" is recorded by 1785. Jazz slang sense of "trumpet" is by 1921. Meaning "telephone" is by 1945. Figurative senses of Latin cornu included "salient point, chief argument; wing, flank; power, courage, strength." Horn of plenty is from 1580s. To make horns at "hold up the fist with the two exterior fingers extended" as a gesture of insult is from c.1600.

Symbolic of cuckoldry since mid-15c. (the victim was fancied to grow one on his head). The image is widespread in Europe and perhaps as old as ancient Greece. The German linguist Hermann Dunger ('Hörner Aufsetzen' und 'Hahnrei', "Germania" 29, 1884) ascribes it to a custom surviving into 19c., "the old practice of engrafting the spurs of a castrated cock on the root of the excised comb, which caused them to grow like horns" [James Hastings, "Encyclopedia of Religion and Ethics"] but the image could have grown as well from a general gesture of contempt or insult made to wronged husbands, "who have been the subject of popular jest in all ages" [Hastings].