1725, "boy who tends to cows and drives them to and from pasture," from cow (n.) + boy.

American-English sense of "man employed to have care of grazing cattle on the Great Plains for a stockman or ranch, doing his work on horseback" is by 1849. Earlier it was an insulting name for a band of marauding loyalists in the neighborhood of New York during the Revolution (1775). In figurative use by 1942 for "brash and reckless young man" (as an adjective meaning "reckless," from 1920s).

The oldest word for "one whose occupation is the care of cattle" is cowherd (late Old English). Cowhand is first attested 1852 in American English (see hand (n.)). Cowpoke (said to be 1881, not in popular use until 1940s) was said to be originally restricted to those who prodded cattle onto railroad cars with long poles. Cowboys and Indians as a children's game (imitating movie serials, etc.) is by 1941.

Proto-Indo-European root meaning "ox, bull, cow," perhaps ultimately imitative of lowing; compare Sumerian gu, Chinese ngu, ngo "ox."

It forms all or part of: beef; Boeotian; Bosphorus; boustrophedon; bovine; bugle; Bucephalus; bucolic; buffalo; bugloss; bulimia; butane; butter; butyl; butyric; cow (n.); cowbell; cowboy; cowlick; cowslip; Euboea; Gurkha; hecatomb; kine.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit gaus, Greek bous, Latin bos, Old Irish bo, Latvian guovs, Armenian gaus, Old English cu, German Kuh, Old Norse kyr, Slovak hovado "cow, ox."

In Germanic and Celtic, of females only; in most other languages, of either gender. For "cow" Latin uses bos femina or vacca, a separate word of unknown origin. Other "cow" words sometimes are from roots meaning "horn, horned," such as Lithuanian karvė, Old Church Slavonic krava.

"cowboy," 1907, American English, earlier buckayro (1889), bakhara (1827), from Spanish vaquero "cowboy," from vaca "cow," from Latin vacca, a word of uncertain origin. The spelling was altered by influence of buck (n.1).

1826, from Spanish, literally "cowboy," from vaca "cow," from Latin vacca "cow," a word of uncertain origin.

"dirty, gross, greasy and messy," 1968, North American colloquial, perhaps a blend of scummy and fuzzy [Barnhart, OED]. First attested use is in reference to Ratso Rizzo in "Midnight Cowboy."

also drug-store, 1810, American English, "pharmacy, store that sells medications and related products," from drug (n.) + store (n.). Drug-store cowboy is 1925, American English slang, originally someone who dressed like a Westerner but obviously wasn't.

1690s, "to furnish with horns," from horn (n.). Earlier in figurative sense of "to cuckold" (1540s). Meaning "to push with the horns" (of cattle, buffalo, etc.) is from 1851, American English; phrase horn in "intrude" is by 1880, American English, originally cowboy slang. Related: Horned; horning.

late 14c., from sun (n.) + set (v.). Perhaps from a Middle English subjunctive such as before the sun set. Old English had sunnansetlgong "sunset," while sunset meant "west." Figurative use from c. 1600. To ride off into the sunset (1963) is from the stereotypical ending of cowboy movies.

1610s, American Spanish, "prairie; treeless, level plain," especially that of South America north of the Amazon, from noun use of Spanish llano "plain, even, level, smooth," ultimately from Latin planus "smooth, flat, level" (from PIE root *pele- (2) "flat; to spread"). Hence llanero "Latin-American cowboy" (1819), literally "plainsman."

1844 (earlier stampedo, 1839), "A general scamper of animals on the Western prairies, generally caused by a fright" [Bartlett], from Mexican Spanish estampida, from Spanish, "an uproar," from estamper "to stamp, press, pound," from Provençal estampier "to stamp," from the same Germanic root that yielded English stamp (v.). The political sense is recorded by 1846 (in reference to the U.S. Democratic Party convention of 1844). As the name of an annual exhibition of cowboy skills in Calgary, Alberta, Canada, it is attested from 1912.