In a way that shows great skill and knowledge; done with the competence of an expert.
From 'expert' (via Old French from Latin 'expertus,' meaning tried or tested) plus the adverbial suffix '-ly.' The word crystallized in its modern form in the 17th century.
The word 'expert' comes from Latin 'expertus,' which literally means 'tested' or 'tried'—so an expert is literally someone who has been tested by experience and proved themselves! It reminds us that expertise requires actual practice, not just knowledge.
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