sheepskin vs credential

sheepskin and credential both are nouns.

Word	Noun	Adjective	Verb	Adverb
sheepskin	Yes	No	No	No
credential	Yes	No	No	No

As nouns, credential is a hypernym of sheepskin; that is, credential is a word with a broader meaning than sheepskin:

sheepskin: a document certifying the successful completion of a course of study
credential: a document attesting to the truth of certain stated facts

Other hypernyms of sheepskin include certificate, certification, credentials.

sheepskin (noun)	credential (noun)
a document certifying the successful completion of a course of study	a document attesting to the truth of certain stated facts
tanned skin of a sheep with the fleece left on; used for clothing
skin of a sheep or goat prepared for writing on