In a very intense, aggressive, or passionate way; with great force or emotion.
From Old French 'fiers', meaning fierce or proud, derived from Latin 'ferus' (wild). The adverbial '-ly' suffix was added to create the adverb form.
Animals fight fiercely to protect their young, which is why 'fiercely protective' became a common phrase—it taps into something primal about defending what matters. Even in modern life, we use the word for dedicated athletes or passionate activists.
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