body odour vs foulness

body odour and foulness both are nouns.

Word	Noun	Adjective	Verb	Adverb
body odour	Yes	No	No	No
foulness	Yes	No	No	No

As nouns, foulness is a hypernym of body odour; that is, foulness is a word with a broader meaning than body odour:

Other hypernyms of body odour include fetidness, malodorousness, rankness, stinkiness.

body odour (noun)	foulness (noun)
malodorousness resulting from a failure to bathe	the attribute of having a strong offensive smell
	(of weather) the badness of the weather
	a state characterized by foul or disgusting dirt and refuse
	disgusting wickedness and immorality