In a dusky manner; in a twilight-like or dim way (an alternative form to 'duskily').
From 'dusk' plus the adverb-forming suffix '-ly,' though this represents an alternate formation alongside 'duskily.' Both forms existed in older English, though 'duskily' became more standard.
This variant shows how English speakers experimented with word forms—'duskly' competes with 'duskily' for the same meaning, and most dialects standardized on 'duskily,' leaving 'duskly' as an archaic variant.
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