sad: [OE] Originally, to feel sad was to feel that one had had ‘enough’. For the word comes ultimately from the same Indo-European base that produced English satisfy and saturate. By the time it reached English (via a prehistoric Germanic *sathaz) ‘enough’ had already become extended to ‘weary’, and the modern sense ‘unhappy’ emerged in the 14th century.
The original notion of ‘sufficiency’ has now died out in the case of sad, but it survives in the case of sated [17], an alteration (probably under the influence of satiate) of the past participle of an earlier verb sade ‘satiate’, which was derived from sad. => sated, satiate, satisfy, saturate
sad (adj.)
Old English s?d "sated, full, having had one's fill (of food, drink, fighting, etc.), weary of," from Proto-Germanic *sathaz (cognates: Old Norse saer, Middle Dutch sat, Dutch zad, Old High German sat, German satt, Gothic sats "satiated, sated, full"), from PIE *seto- (cognates: Latin satis "enough, sufficient," Greek hadros "thick, bulky," Old Church Slavonic sytu, Lithuanian sotus "satiated," Old Irish saith "satiety," sathach "sated"), from root *sa- "to satisfy" (cognates: Sanskrit a-sinvan "insatiable").
Sense development passed through the meaning "heavy, ponderous" (i.e. "full" mentally or physically), and "weary, tired of" before emerging c. 1300 as "unhappy." An alternative course would be through the common Middle English sense of "steadfast, firmly established, fixed" (as in sad-ware "tough pewter vessels") and "serious" to "grave." In the main modern sense, it replaced Old English unrot, negative of rot "cheerful, glad."
Meaning "very bad" is from 1690s. Slang sense of "inferior, pathetic" is from 1899; sad sack is 1920s, popularized by World War II armed forces (specifically by cartoon character invented by Sgt. George Baker, 1942, and published in U.S. Armed Forces magazine "Yank"), probably a euphemistic shortening of common military slang phrase sad sack of shit.
例文
1. This condition is called seasonal affective disorder，or SAD for short.
この病状を季節性感情失調症、または SAD と略称する。
2. Guy Powell, defending, told magistrates: "It's a sad and disturbing case.「
ガイ?パウエル氏は弁護中に地方裁判官に「非常に不幸で不安な事件だ」と述べた。
3.I 'm sad about my toys getting burned in the fire.
私のおもちゃがこの火の中で燃えてしまったのは悲しいです。
4.He died five or six years ago I 'm sad to say.
残念ながら、彼は5、6年前に亡くなりました。
5.How can anyone look sad at an occasion like this？