The quality or state of being stupid or lacking in intelligence.
Noun form of 'fatheaded,' created by adding the -ness suffix, a productive suffix in English for converting adjectives into abstract nouns. The word emerged in the 19th century alongside the adjective.
Creating nouns about character flaws with -ness (like stupidity, kindness, rudeness) lets us talk about abstract qualities—it's why English has so many words for personality traits compared to many other languages.
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