The story
From light-headed (adjective) (any sense) + -ly (suffix forming adverbs).
Etymology from Wiktionary, CC BY-SA 4.0.
light-headedly
light·head·ed·lyToday it means: In a light-headed manner; with a light head. Full definition →
Today it means: In a light-headed manner; with a light head. Full definition →
From light-headed (adjective) (any sense) + -ly (suffix forming adverbs).
Etymology from Wiktionary, CC BY-SA 4.0.