cowpuncher vs buckeroo

cowpuncher and buckeroo both are nouns.

Word	Noun	Adjective	Verb	Adverb
cowpuncher	Yes	No	No	No
buckeroo	Yes	No	No	No

As nouns, buckeroo is a hyponym of cowpuncher; that is, buckeroo is a word with a more specific, narrower meaning than cowpuncher:

cowpuncher: a hired hand who tends cattle and performs other duties on horseback
buckeroo: local names for a cowboy (`vaquero' is used especially in southwestern and central Texas and `buckaroo' is used especially in California)

Other hyponyms of cowpuncher include buckaroo, vaquero, cowgirl, gaucho, horse wrangler, wrangler, roper, cattleman, cowboy, cowman.

cowpuncher (noun)	buckeroo (noun)
a hired hand who tends cattle and performs other duties on horseback	local names for a cowboy (`vaquero' is used especially in southwestern and central Texas and `buckaroo' is used especially in California)