In a darling manner; affectionately, sweetly, or in the manner of a beloved person or thing.
From 'darling' (a term of endearment from Old English 'deore' meaning dear) + the adverbial suffix '-ly'. This creates an adverb expressing affectionate or loving quality.
Though 'darlingly' is grammatically correct, it's almost never used—we prefer the standalone 'darling' as an adjective ('a darling smile') because '-ly' adverbs sound awkward with emotional words.
Complete word intelligence in one call. Free tier — 50 lookups/day.