timidness vs diffidence

timidness and diffidence both are nouns.

Word	Noun	Adjective	Verb	Adverb
timidness	Yes	No	No	No
diffidence	Yes	No	No	No

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

Other hyponyms of timidness include cold feet, shyness, self-distrust, self-doubt.

timidness (noun)	diffidence (noun)
fear of the unknown or unfamiliar or fear of making decisions	lack of self-confidence