In a manner that adorns or serves to decorate; in a beautifying way.
From adorning (present participle) + -ly (adverbial suffix), creating an adverb that describes how an action is performed in an adorning manner.
This is a rare adverb that's almost never used in modern English, showing how language evolves—we've abandoned many Victorian-era adverbs that tried to turn every adjective into a modifiable form.
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