foulness vs fetidness

foulness and fetidness both are nouns.

Word	Noun	Adjective	Verb	Adverb
foulness	Yes	No	No	No
fetidness	Yes	No	No	No

As nouns, foulness and fetidness are synonyms defined as:

foulness and fetidness: the attribute of having a strong offensive smell

Other synonyms of foulness include malodorousness, rankness, stinkiness.

foulness (noun)	fetidness (noun)
the attribute of having a strong offensive smell	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