Our Living Language Cowboys and the Wild West are indelibly set in the minds of many as typical of Americaan association borne out by several common Modern English words that originated in the speech of the 19th-century western United States. One is dude, now perhaps most familiar as a slang term with a wide range of uses (including use as an all-purpose interjection for expressing approval: “Dude!”). Originally it was applied to fancy-dressed city folk who went out west on vacation. In this usage it first appears in the 1870s. The origin of the word is not known, but a number of other cowboy terms were borrowed by early settlers from American Spanish. These include buckaroo, corral, lasso, mustang, ranch, rodeo, and stampede. Buckaroo, interestingly, is an example of a word borrowed twice: it is an Americanized form of Spanish vaquero, which also made it into English as vaquero, a cowboy.
thats from dictionary.com. i have to ask my little sister where she found that definition. she showed it to me like 4 months ago and has been calling me and my bro dudes ever since.