buckaroo vs cowherd

buckaroo and cowherd both are nouns.

Word	Noun	Adjective	Verb	Adverb
buckaroo	Yes	No	No	No
cowherd	Yes	No	No	No

As nouns, cowherd is a hypernym of buckaroo; that is, cowherd is a word with a broader meaning than buckaroo:

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

Other hypernyms of buckaroo include cowhand, cowpoke, cowpuncher, puncher.

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