sheepherder vs herdsman

sheepherder and herdsman both are nouns.

Word	Noun	Adjective	Verb	Adverb
sheepherder	Yes	No	No	No
herdsman	Yes	No	No	No

As nouns, herdsman is a hypernym of sheepherder; that is, herdsman is a word with a broader meaning than sheepherder:

sheepherder: a herder of sheep (on an open range); someone who keeps the sheep together in a flock
herdsman: someone who drives a herd

Other hypernyms of sheepherder include drover, herder.

sheepherder (noun)	herdsman (noun)
a herder of sheep (on an open range); someone who keeps the sheep together in a flock	someone who drives a herd