fervour vs feverishness

fervour and feverishness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fervour	Yes	No	No	No
feverishness	Yes	No	No	No

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

Other hyponyms of fervour include fever, fever pitch, sensation.

fervour (noun)	feverishness (noun)
feelings of great warmth and intensity	a rise in the temperature of the body; frequently a symptom of infection
the state of being emotionally aroused and worked up	A state of wildly excited activity or emotion.