Ridiculousness is a related term of fatuousness.
As nouns the difference between ridiculousness and fatuousness
is that ridiculousness is (uncountable) the characteristic of being ridiculous while fatuousness is the characteristic of being fatuous.
ridiculousness
English
Noun
(uncountable) The characteristic of being ridiculous.
(countable) The result of being ridiculous.
Synonyms
* ridiculosity (less common)
fatuousness
English
Noun
(en-noun)
The characteristic of being fatuous.