grimness vs severeness

grimness and severeness both are nouns.

Word	Noun	Adjective	Verb	Adverb
grimness	Yes	No	No	No
severeness	Yes	No	No	No

As nouns, grimness and severeness are synonyms defined as:

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

grimness (noun)	severeness (noun)
something hard to endure	extreme plainness
the quality of being ghastly	excessive sternness
	something hard to endure
	used of the degree of something undesirable e.g. pain or weather