chest vs treasure chest

chest and treasure chest both are nouns.

Word	Noun	Adjective	Verb	Adverb
chest	Yes	No	No	No
treasure chest	Yes	No	No	No

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

chest (noun)	treasure chest (noun)
box with a lid; used for storage; usually large and sturdy	a chest filled with valuables
furniture with drawers for keeping clothes
the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates
the front of the trunk from the neck to the abdomen