The quality or state of being beastly; cruelty, savagery, or animal-like behavior.
From 'beastly' (adjective, from Old French 'beste') plus '-ness', creating an abstract noun that names the quality itself rather than a specific instance of it.
Medieval monks used words like 'beastliness' to define sin—mapping animal behaviors onto moral failings created a whole vocabulary of animal-based insults that still haunts English (calling someone a 'pig,' 'snake,' or 'wolf').
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