accessory vs key fob

accessory and key fob both are nouns.

Word	Noun	Adjective	Verb	Adverb
accessory	Yes	Yes	No	No
key fob	Yes	No	No	No

As nouns, key fob is a hyponym of accessory; that is, key fob is a word with a more specific, narrower meaning than accessory:

accessory: clothing that is worn or carried, but not part of your main clothing
key fob: A small object fastened to a key chain or key ring and designed to be comfortably grasped.

Other hyponyms of accessory include belt, furnishing, trappings, keyfob.

accessory (noun)	key fob (noun)
a supplementary component that improves capability	A small object fastened to a key chain or key ring and designed to be comfortably grasped.
clothing that is worn or carried, but not part of your main clothing
someone who helps another person commit a crime

accessory (adjective)	key fob (adjective)
furnishing added support
aiding and abetting in a crime