rigorousness vs rigourousness

rigorousness and rigourousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
rigorousness	Yes	No	No	No
rigourousness	Yes	No	No	No

As nouns, rigorousness and rigourousness are synonyms defined as:

Other synonyms of rigorousness include asperity, grimness, hardship, rigor, rigour, severeness, severity.

As nouns, rigorousness and rigourousness are synonyms defined as:

Other synonyms of rigorousness include hardness, harshness, inclemency, rigor, rigour, severeness, severity, stiffness.

rigorousness (noun)	rigourousness (noun)
something hard to endure	something hard to endure
excessive sternness	excessive sternness