RIGOROUSNESS
severity, severeness, harshness, rigor, rigour, rigorousness, rigourousness, inclemency, hardness, stiffness
(noun) excessive sternness; “severity of character”; “the harshness of his punishment was inhuman”; “the rigors of boot camp”
asperity, grimness, hardship, rigor, rigour, severity, severeness, rigorousness, rigourousness
(noun) something hard to endure; “the asperity of northern winters”
Source: WordNet® 3.1
Etymology
Noun
rigorousness (usually uncountable, plural rigorousnesses)
The property of being rigorous, strictness.
Source: Wiktionary