In a frightened or scared manner; with fear or in a way that shows someone is afraid.
From 'frightened' (past participle of 'frighten') plus the adverbial suffix '-ly,' creating an adverb that describes how something is done with fear.
While grammatically correct, 'frightenedly' is rarely used in modern English because 'fearfully' or 'in fear' sound more natural, showing how some words are technically possible but practically abandoned.
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