Carefully

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Old English carful (see care, -ful).

wiktionary

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From Middle English carfulli, carefulliche, from Old English carfullīċe, ċearfullīċe(“carefully, diligently”), equivalent to careful +‎ -ly.

etymonline

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carefully (adv.)

Old English carfullice "sorrowfully;" see careful + -ly (2). Meaning "heedfully" is in late Old English.