Etymology
Advertisement
afternoon (n.)

"part of the day from noon to evening," c. 1300, from after + noon. In 15c.-16c., the form was at afternoon; from c. 1600 it has been in the afternoon. As an adjective from 1570s. Middle English had also aftermete "afternoon, part of the day following the noon meal" (mid-14c.).

Related entries & more 
Advertisement
mid-afternoon (n.)

"the middle of the afternoon," c. 1400, from mid (adj.) + afternoon. Earlier in the same sense was mid-overnoon (late 13c.).

Related entries & more 
matinee (n.)

"afternoon performance, an entertainment held in the daytime," 1848, from French matinée (musicale), from matinée "morning" (with a sense here of "daytime"), from matin "morning" (but here "afternoon" or "daytime"), from Old French matines (see matins). Originally as a French word in English; it lost its foreignness by late 19c. For the French suffix, compare journey.

Related entries & more 
nuncheon (n.)

mid-14c., nōn-schench, "slight refreshment of food and/or liquor taken at midday," originally taken in the afternoon, from none "noon" (see noon) + shench "draught, cup," from Old English scenc, related to scencan "to pour out, to give to drink," cognate with Old Frisian skenka "to give to drink, German, Dutch schenken "to give." Compare luncheon.

Related entries & more 
undern (n.)
an obsolete Old English and Middle English word for "morning;" in Old English originally "third hour of the day; 9 a.m." (corresponding to tierce). Hence underngeweorc, undernmete "breakfast." Common Germanic: Old Frisian unden, Old Saxon undorn, Middle Dutch onderen, Old High German untarn, Old Norse undorn; of uncertain origin. By extension, "period from 9 a.m. to noon;" but from 13c. shifting to "midday, noon" (as in undern-mete "lunch," 14c.); and by late 15c. to "late afternoon or early evening."
Related entries & more 
Advertisement
cenacle (n.)

"dining room," usually with reference to the room in which the Last Supper was held, c. 1400, from Old French cenacle, learned variant of cenaille (14c., Modern French cénacle), from Latin cenaculum "dining room," from cena "mid-day meal, afternoon meal," literally "portion of food," from PIE *kert-sna-, from root *sker- (1) "to cut." Latin cenaculum was used in the Vulgate for the "upper room" where the Last Supper was eaten. Related: Cenatical; cenation.

Related entries & more 
luncheon (n.)
"light repast between mealtimes," 1650s (lunching; spelling luncheon by 1706); earlier "thick piece, hunk (of bread)," 1570s (luncheon), which is of uncertain origin. Perhaps it is based on northern English dialectal lunch "hunk of bread or cheese" (1580s; said to be probably from Spanish lonja "a slice," literally "loin"), blended with or influenced by nuncheon (Middle English nonechenche, mid-14c.) "light mid-day meal," from none "noon" (see noon) + schench "drink," from Old English scenc, from scencan "pour out."

Despite the form lunching in the 1650s source OED discounts that it possibly could be from lunch (v.), which is first attested more than a century later. It suggests perhaps an analogy with truncheon, etc., or to simulate a French origin. Especially in reference to an early afternoon meal eaten by those who have a noontime dinner.
Related entries & more 
cojones (n.)

"courage," literally "testicles, balls," 1932, in Hemingway ("Death in the Afternoon," an account of Spanish bull-fighting), from Spanish cojon "testicle," from Latin coleus "the testicles" (source of Italian coglione), literally "strainer bag," a variant of culleus "a leather sack," cognate with Greek koleos "sheath of a sword, scabbard." Both are said in some sources to be from PIE root *kel- (1) "to cover, conceal, save," but de Vaan finds it "Probably a loanword from a non-IE language, independently into Latin and Greek."

English had it as cullion a 16c. term of contempt for a man, "a mean wretch" (Shakespeare) also "a testicle" (Chaucer), from Middle English coujon, coilon (late 14c.), from Old French coillon "testicle; worthless fellow, dolt," from Latin coleus. 

Related entries & more 
breakfast (n.)

"first meal of the day," mid-15c., from the verbal phrase; see break (v.) + fast (n.). For vowel shift, see below. An Old English word for it was undernmete (see undern), also morgenmete "morning meal."

Spanish almuerzo "lunch," but formerly and still locally "breakfast," is from Latin admorsus, past participle of admordere "to bite into," from ad "to" + mordēre "to bite" (see mordant). German Frühstück is from Middle High German vruostücke, literally "early bit."

In common with almuerzo, words for "breakfast" tend over time to shift in meaning toward "lunch;" compare French déjeuner "breakfast," later "lunch" (cognate of Spanish desayuno "breakfast"), from Vulgar Latin *disieiunare "to breakfast," from Latin dis- "apart, in a different direction from" + ieiunare, jejunare "fast" (see jejune; also compare dine). Greek ariston in Homer and Herodotus was a meal at the break of day but in classical times taken in the afternoon.

The long/short vowel contrast in break/breakfast represents a common pattern where words from Old English have a long vowel in their modern form but a short vowel as the first element of a compound: Christ/Christmas, holy/holiday, moon/Monday, sheep/shepherd, wild/wilderness, etc.

Related entries & more 
moment (n.)

late 14c., "very brief portion of time, instant," in moment of time, from Old French moment (12c.) "moment, minute; importance, weight, value" and directly from Latin momentum "movement, motion; moving power; alteration, change;" also "short time, instant" (also source of Spanish, Italian momento), contraction of *movimentum, from movere "to move" (from PIE root *meue- "to push away").

Some (but not OED) explain the sense evolution of the Latin word by notion of a particle so small it would just "move" the pointer of a scale, which led to the transferred sense of "minute time division."

In careful use, a moment has duration, an instant does not. The sense of "notable importance, 'weight,' value, consequence" is attested in English from 1520s. Meaning "opportunity" (as in seize the moment) is from 1781.

In for the moment "temporarily, so far as the near future is concerned" (1883) it means "the present time." Phrase never a dull moment is attested by 1885 (Jerome K. Jerome, "On the Stage - and Off"). Phrase moment of truth first recorded 1932 in Hemingway's "Death in the Afternoon," from Spanish el momento de la verdad, the final sword-thrust in a bull-fight.

Related entries & more