Aloud

google

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Middle English: from a-2 (expressing manner) + loud.

wiktionary

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From Middle English aloud, a loude(“aloud”), equivalent to a- +‎ loud or a- +‎ loude(“sound”).

etymonline

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aloud (adv.)

late 13c., "with a loud voice;" c. 1300, "audibly, not whispered;" contraction of on loude; see a- (1) + loud.