jewelry vs bling bling

jewelry and bling bling both are nouns.

Word	Noun	Adjective	Verb	Adverb
jewelry	Yes	No	No	No
bling bling	Yes	No	No	No

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

jewelry: an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)
bling bling: flashy, ostentatious jewelry

jewelry (noun)	bling bling (noun)
an adornment (as a bracelet or ring or necklace) made of precious metals and set with gems (or imitation gems)	flashy, ostentatious jewelry