jewel casket vs casket

jewel casket and casket both are nouns.

Word	Noun	Adjective	Verb	Adverb
jewel casket	Yes	No	No	No
casket	Yes	No	Yes	No

As nouns, jewel casket and casket are synonyms defined as:

jewel casket and casket: small and often ornate box for holding jewels or other valuables

jewel casket (noun)	casket (noun)
small and often ornate box for holding jewels or other valuables	small and often ornate box for holding jewels or other valuables
	box in which a corpse is buried or cremated

jewel casket (verb)	casket (verb)
	enclose in a casket