In a hallowed or sanctified manner; in a way that shows reverence for something holy.
From 'hallowed' (past participle of 'hallow') with the -ly adverbial suffix, creating a manner adverb from the adjective meaning 'made sacred.'
The -ly suffix is the most productive word-making tool in English—you can stick it on nearly any adjective to make an adverb, and 'hallowedly' shows how productive it is, even for archaic words.
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