hardiness vs hardihood

hardiness and hardihood both are nouns.

Word	Noun	Adjective	Verb	Adverb
hardiness	Yes	No	No	No
hardihood	Yes	No	No	No

As nouns, hardiness and hardihood are synonyms defined as:

hardiness and hardihood: the trait of being willing to undertake things that involve risk or danger

Other synonyms of hardiness include boldness, daring.

hardiness (noun)	hardihood (noun)
the property of being strong and healthy in constitution	the trait of being willing to undertake things that involve risk or danger
the trait of being willing to undertake things that involve risk or danger