In a balmy manner; warmly and pleasantly, or in a foolish or silly way (British slang).
From 'balmy' plus the adverbial suffix '-ly,' creating an adverb that modifies verbs and adjectives. The multiple meanings follow from balmy's dual sense.
When you describe something happening 'balmily,' you're painting a picture—either of pleasant, warm, gentle conditions or, in British slang, of complete silliness and foolishness.
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