The quality or state of being felonious; the character or nature of serious criminal behavior involving treachery or wickedness.
From 'felonious' plus '-ness' suffix creating an abstract noun. Combines Old French 'felon' with Germanic suffixes to create a legal-moral abstraction.
English law distinguishes 'feloniousness' from simple illegality—it's the difference between accidentally breaking a law and deliberately committing an act of moral corruption.
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