In a careful, watchful, and protective manner; with close attention to safety or security.
Formed from guardful (guard + -ful) plus the adverbial suffix -ly, which converts adjectives to adverbs describing how an action is performed. Traces back to Old French garder and Germanic 'ward.'
Stacking suffixes like this (guard → guardful → guardfully) shows English's incredible flexibility, though the word sounds archaic now—we'd more likely say 'carefully' or 'protectively' in modern usage.
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