careeryoudaoicibaDictYouDict[career 词源字典]
career: [16] Originally, a career was a ‘road or racetrack for vehicles’. Its ultimate source was Latin carrus ‘wheeled vehicle’ (from which we get car), which produced the Vulgar Latin derivative *carāria ‘track for wheeled vehicles’. This passed into English via Provençal carreira, Italian carriera, and French carrière. Its earliest meaning was ‘racecourse’, and hence, by extension, ‘swift course’; the main present-day sense ‘course of someone’s working life’ did not develop until the 19th century, probably owing to renewed influence of French carrière.
=> car[career etymology, career origin, 英语词源]
stadiumyoudaoicibaDictYouDict
stadium: [16] Greek stádion denoted a ‘racetrack’, particularly the one at Olympia, which was about 185 metres long. In due course the word came to be used as a term for a measure of length equal to this, and that was the sense in which English originally acquired it, via Latin stadium. The original ‘racetrack’ was introduced in the 17th century, and ‘sports arena’ is a modern development of this. The Greek word itself was an alteration of an earlier spádion ‘racetrack’, a derivative of span ‘pull’ (source of English spasm). The change from sp- to st- was perhaps set in motion by Greek stádios ‘fixed, firm’.
=> spasm
horse (n.)youdaoicibaDictYouDict
Old English hors, from Proto-Germanic *hursa- (cognates: Old Norse hross, Old Frisian hors, Middle Dutch ors, Dutch ros, Old High German hros, German Roß "horse"), of unknown origin, connected by some with PIE root *kurs-, source of Latin currere "to run" (see current (adj.)).

The usual Indo-European word is represented by Old English eoh, from PIE *ekwo- "horse" (see equine). In many other languages, as in English, this root has been lost in favor of synonyms, probably via superstitious taboo on uttering the name of an animal so important in Indo-European religion.

Used since at least late 14c. of various devices or appliances which suggest a horse (as in sawhorse). To ride a horse that was foaled of an acorn (1670s) was through early 19c. a way to say "be hanged from the gallows." Slang for heroin is first attested 1950. Horse latitudes first attested 1777, the name of unknown origin, despite much speculation. Dead horse as a figure for "something that has ceased to be useful" is attested from 1630s.
HORSEGODMOTHER, a large masculine wench; one whom it is difficult to rank among the purest and gentlest portion of the community. [John Trotter Brockett, "A Glossary of North Country Words," 1829]
The horse's mouth as a source of reliable information is from 1921, perhaps originally of racetrack tips, from the fact that a horse's age can be determined accurately by looking at its teeth. To swap horses while crossing the river (a bad idea) is from the American Civil War and appears to have been originally one of Abe Lincoln's stories. Horse and buggy meaning "old-fashioned" is recorded from 1926 slang, originally in reference to a "young lady out of date, with long hair."