bitter pecan vs hickory

bitter pecan and hickory both are nouns.

Word	Noun	Adjective	Verb	Adverb
bitter pecan	Yes	No	No	No
hickory	Yes	No	No	No

As nouns, hickory is a hypernym of bitter pecan; that is, hickory is a word with a broader meaning than bitter pecan:

bitter pecan: hickory of southern United States having many narrow leaflets and rather bitter nuts
hickory: American hardwood tree bearing edible nuts

Other hypernyms of bitter pecan include hickory tree.

bitter pecan (noun)	hickory (noun)
hickory of southern United States having many narrow leaflets and rather bitter nuts	American hardwood tree bearing edible nuts
	valuable tough heavy hardwood from various hickory trees