precordium vs external organ

precordium and external organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
precordium	Yes	No	No	No
external organ	Yes	No	No	No

As nouns, external organ is a hypernym of precordium; that is, external organ is a word with a broader meaning than precordium:

precordium: the external surface of the body overlying the heart and stomach
external organ: an organ that is situated on or near the surface of the body

precordium (noun)	external organ (noun)
the external surface of the body overlying the heart and stomach	an organ that is situated on or near the surface of the body